feat(web): persist validated browser panel layouts (#2258)

* xtask: the test suite and clippy pass on Windows

Two Windows-only failures stopped `cargo xtask ci` before it got going on
a Windows checkout (CI runs the gate on Linux only, so neither showed):

- parity::tests::civil_dates built a SystemTime 115,740,740 days after
  the epoch (year 318857). Windows' SystemTime ends in the year 30828, so
  the addition panicked ("overflow when adding duration to `SystemTime`").
  That case now checks `civil_from_days` on the day count, which is what
  it was about, on every platform.
- stats.rs imported `walk` for a test that only exists on Unix, so the
  import was unused on Windows and `clippy -D warnings` refused it. The
  Unix test calls `super::walk`, as its neighbour calls `super::walk_inner`.

Checked on Windows 11 x64: `cargo test --workspace` and
`cargo clippy --workspace --all-targets -- -D warnings` both pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* feat(web): persist validated browser panel layouts

CC-053: keep embedded floating, docked and hidden panels across reloads
through the existing host save cycle. Reject malformed/versioned records
atomically; native workspaces and drawings remain unchanged.

Validation: all seven cargo xtask ci gates passed (2558 pass, 0 fail,
1 ignored) on a2dd814 plus this exact change. Actual release Trunk bundle
and Edge floating/close/reload/reset/reload passed. Forced WebGL startup,
render and recovered layout passed; full edit cycle used default mode.

Dependency: original #2198 Windows test prerequisite. No #2226 dependency.
Revert this commit independently to stop using the optional storage key.
Upstream c3b8e7b adds nextest minimum configuration only; no runtime overlap.

---------

Co-authored-by: 2ez4gcx <108074836+2ez4gcx@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

apps/cadcraft-web/src/main.rs

@@ -14,6 +14,9 @@ pub mod download;
 #[cfg(target_arch = "wasm32")]
 mod host;
 
+#[cfg(any(target_arch = "wasm32", test))]
+mod panel_layout;
+
 #[cfg(target_arch = "wasm32")]
 mod web {
     use cadcraft_engine::Session;
@@ -59,10 +62,14 @@ mod web {
             self.0.raw_input_hook(ctx, raw);
             cadcraft_ui_egui::cmdline::capture_tab(ctx, raw);
         }
-        /// Preferences (interface theme and language) survive reloads; egui state is not kept.
+        /// Preferences and validated panel placement survive reloads; egui memory is not kept.
         fn save(&mut self, storage: &mut dyn eframe::Storage) {
             storage.set_string(cadcraft_ui_egui::options::PROFILE_KEY, self.0.profile_json());
             storage.set_string(cadcraft_ui_egui::PREFS_KEY, self.0.prefs_json());
+            match crate::panel_layout::save(&self.0.ui) {
+                Ok(layout) => storage.set_string(crate::panel_layout::KEY, layout),
+                Err(error) => log::warn!("panel layout was not saved: {error}"),
+            }
         }
         fn persist_egui_memory(&self) -> bool {
             false
@@ -160,6 +167,11 @@ mod web {
                         if let Some(prefs) = cc.storage.and_then(|s| s.get_string(cadcraft_ui_egui::PREFS_KEY)) {
                             app.load_prefs(&prefs);
                         }
+                        if let Some(layout) = cc.storage.and_then(|s| s.get_string(crate::panel_layout::KEY))
+                            && let Err(error) = crate::panel_layout::restore(&mut app.ui, &layout)
+                        {
+                            log::warn!("panel layout was not restored: {error}");
+                        }
                         // `?cpu`: no render state for the app, so the canvas draws with egui shapes.
                         if !crate::wants_cpu(&query())
                             && let Some(rs) = &cc.wgpu_render_state

apps/cadcraft-web/src/panel_layout.rs

@@ -0,0 +1,104 @@
+//! Browser panel layout storage, independent of drawings and native workspace files.
+
+use cadcraft_ui_egui::{UiState, docking};
+use serde_json::{Value, json};
+
+#[cfg(target_arch = "wasm32")]
+pub const KEY: &str = "cadcraft.panel-layout";
+const MAX_BYTES: usize = 64 * 1024;
+
+/// Serialize only validated panel placement and visibility, with a bounded record size.
+pub fn save(ui: &UiState) -> Result<String, String> {
+    docking::validate(&ui.docking)?;
+    let saved = json!({
+        "version": docking::LAYOUT_VERSION,
+        "docking": ui.docking,
+        "showToolsets": ui.show_toolsets,
+        "showPalettes": ui.show_palettes,
+    })
+    .to_string();
+    if saved.len() > MAX_BYTES {
+        return Err("panel layout exceeds 64 KiB".into());
+    }
+    Ok(saved)
+}
+
+/// Validate the entire optional record before changing any UI field.
+pub fn restore(ui: &mut UiState, saved: &str) -> Result<(), String> {
+    if saved.len() > MAX_BYTES {
+        return Err("panel layout exceeds 64 KiB".into());
+    }
+    let value: Value = serde_json::from_str(saved).map_err(|error| error.to_string())?;
+    if value.get("version").and_then(Value::as_u64) != Some(u64::from(docking::LAYOUT_VERSION)) {
+        return Err("unsupported panel layout version".into());
+    }
+    let workspace: docking::Workspace =
+        serde_json::from_value(value.get("docking").cloned().ok_or("missing panel layout")?).map_err(|error| error.to_string())?;
+    docking::validate(&workspace)?;
+    let tools = value.get("showToolsets").and_then(Value::as_bool).ok_or("invalid Tool Sets visibility")?;
+    let palettes = value.get("showPalettes").and_then(Value::as_bool).ok_or("invalid palette visibility")?;
+    ui.docking = workspace;
+    ui.show_toolsets = tools;
+    ui.show_palettes = palettes;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use cadcraft_engine::Session;
+    use cadcraft_ui_egui::{CadApp, Services};
+
+    #[test]
+    fn floating_and_hidden_panels_survive_storage_without_replacing_drawing_state() {
+        let mut source = CadApp::new(Session::default(), Services::default());
+        source.run("ui.dock", json!({"operation":"float","panel":"toolSets","rect":[120,90,340,410]})).unwrap();
+        source.run("ui.dock", json!({"operation":"close","panel":"properties"})).unwrap();
+        let saved = save(&source.ui).unwrap();
+        let mut destination = CadApp::new(Session::default(), Services::default());
+        destination.session.start("line").unwrap();
+        let before = destination.session.doc().unwrap().clone();
+        restore(&mut destination.ui, &saved).unwrap();
+        assert_eq!(destination.ui.docking, source.ui.docking);
+        assert_eq!(destination.ui.show_toolsets, source.ui.show_toolsets);
+        assert_eq!(destination.ui.show_palettes, source.ui.show_palettes);
+        assert_eq!(destination.session.running.as_ref().map(|command| command.id.as_str()), Some("line"));
+        assert_eq!(destination.session.doc().unwrap(), &before);
+    }
+
+    #[test]
+    fn malformed_or_unsupported_storage_is_rejected_atomically() {
+        let mut ui = UiState::default();
+        let before = serde_json::to_value(&ui).unwrap();
+        let valid: Value = serde_json::from_str(&save(&ui).unwrap()).unwrap();
+        for (field, bad) in [
+            ("version", json!(0)),
+            ("version", json!(docking::LAYOUT_VERSION + 1)),
+            ("docking", json!({})),
+            ("showToolsets", json!("false")),
+            ("showPalettes", Value::Null),
+        ] {
+            let mut invalid = valid.clone();
+            invalid[field] = bad;
+            assert!(restore(&mut ui, &invalid.to_string()).is_err());
+            assert_eq!(serde_json::to_value(&ui).unwrap(), before);
+        }
+        for invalid in ["not json".to_string(), " ".repeat(MAX_BYTES + 1)] {
+            assert!(restore(&mut ui, &invalid).is_err());
+            assert_eq!(serde_json::to_value(&ui).unwrap(), before);
+        }
+    }
+
+    #[test]
+    fn storage_cannot_remove_the_document_view() {
+        let mut ui = UiState::default();
+        let before = serde_json::to_value(&ui).unwrap();
+        let mut invalid = ui.clone();
+        invalid.docking.layout.root = None;
+        assert!(save(&invalid).is_err());
+        let mut record: Value = serde_json::from_str(&save(&ui).unwrap()).unwrap();
+        record["docking"] = serde_json::to_value(&invalid.docking).unwrap();
+        assert!(restore(&mut ui, &record.to_string()).is_err());
+        assert_eq!(serde_json::to_value(&ui).unwrap(), before);
+    }
+}

docs/ui-parity.md

@@ -1,6 +1,6 @@
 # UI parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-22 · **Change:** minor (distinct polyline midpoint grips) · **Target:** Autodesk AutoCAD 2027 for Mac (26.0)
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-26 · **Change:** minor (browser panel layout storage) · **Target:** Autodesk AutoCAD 2027 for Mac (26.0)
 
 How CADCraft's interaction compares with AutoCAD's: point entry, object snaps, tracking, dynamic
 input, grips, selection, the command line, chrome and navigation. A drafter's speed in AutoCAD
@@ -166,6 +166,7 @@ down-arrow options menu (DYNPROMPT), and DYNDIM.
 | ViewCube | interactive 3D | clickable for 2D (Top/Home → extents); dragging does nothing (#7) |
 | Navigation bar, SteeringWheels | yes | no |
 | Workspaces | Drafting & Annotation, 3D Modeling | no |
+| Browser panel layout storage | not applicable | Versioned, validated panel placement and visibility saved through the browser host; floating palettes remain embedded. Requires available browser storage and a completed host save; named workspaces and drawing persistence are separate. |
 | Options / Preferences dialog | many tabs | **no** (issue #23) |
 | Customisation (CUI, aliases editor, tool palettes) | yes | Command Aliases dialog (ALIASEDIT, #1381); no CUI or tool palettes |
 | Themes | Dark, Light | Dark, Light, System (#179) |
@@ -203,6 +204,7 @@ down-arrow options menu (DYNPROMPT), and DYNDIM.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-26 | minor | Browser host stores bounded, validated panel layout separately from drawing state; malformed or unsupported records retain defaults. Native workspace storage is unchanged. |
 | 2026-10-22 | minor | Polyline segment midpoint grips use rectangles, distinct from square vertex grips, with matching hover and pick bounds (#1950) |
 | 2026-10-13 | minor | Filled-region highlight boundaries are traversed in deterministic coordinate order, fixing dash-phase jumps on CPU hover/selection redraws and GPU highlight rebuilds; CPU dash-position, pixel and GPU mesh regressions |
 | 2026-10-14 | minor | Selection cycling (#1143): the list and badge of SELECTIONCYCLING, Shift+Space through overlapping objects (#1145) |

packaging/web/README.md

@@ -50,6 +50,18 @@ location /cadcraft/ {
 
 Local test: `python3 -m http.server 8765` inside the folder, then open http://localhost:8765/.
 
+## Panel layout storage
+
+The browser host saves docked, floating and hidden palette arrangements alongside interface
+preferences in its local storage. Floating palettes remain embedded in the browser canvas;
+they do not become native operating-system windows. Window > Reset Palettes restores the
+default arrangement. This record contains panel placement and visibility, not drawing data.
+
+The optional `cadcraft.panel-layout` record uses the shared docking layout version and is
+limited to 64 KiB. Malformed, incompatible or invalid arrangements are ignored atomically,
+leaving the startup defaults usable. Storage availability and autosave follow the browser
+host's existing eframe persistence; clearing site data removes the saved layout.
+
 ## Embedding in a page (iframe)
 
 ```html