Docs: where the portable marker goes on macOS, AppImage and Flatpak; keep a portable copy where only you can write (#1366)

docs/control-protocol.md

@@ -12,7 +12,9 @@ logs, recovery and user libraries then use that root, without importing the lega
 An unset override preserves the usual platform paths and legacy migration; an explicitly empty override
 disables those paths. `VECTORCRAFT_NO_PREFS` continues to disable preference reads and writes.
 Without the override, a `portable.txt` or `VectorCraft.portable` file beside the executable (as in the
-Windows portable zip) puts that root in `VectorCraftData` next to the executable.
+Windows portable zip) puts that root in `VectorCraftData` next to the executable; on macOS the marker
+and the folder sit next to `VectorCraft.app`, for an AppImage next to the `.AppImage` file, and a
+Flatpak install has neither. `VECTORCRAFT_NO_PREFS` never looks for the marker or creates the folder.
 
 **Only requests are read.** Every line must be a JSON object with a string `method` (`id` and `params`
 are optional; blank lines are skipped). Anything else gets one error reply

docs/releasing.md

@@ -116,11 +116,18 @@ to the target triple, so host build scripts aren't affected.
 - **Portable zip:** it ships `packaging/windows/portable.txt` beside `vectorcraft.exe`. That
   marker (or a `VectorCraft.portable` file) switches on portable mode, as in PhotoCraft: `ui.json`
   and the folders next to it (Swatches, Graphic Styles, Fonts, Data Recovery, logs…) go to
-  `VectorCraftData\` next to the exe instead of `%APPDATA%\VectorCraft`. If that folder isn't
-  writable the app logs a warning and uses `%APPDATA%`. Deleting `portable.txt` returns settings to
-  the user profile (the `VectorCraftData` folder is left as it is). The MSI has no marker.
-  `VECTORCRAFT_CONFIG_DIR` still wins. The logic is in `apps/vectorcraft/src/profile.rs` and works
-  the same on macOS and Linux.
+  `VectorCraftData\` next to the exe instead of `%APPDATA%\VectorCraft`. The first time
+  `VectorCraftData` is created, the settings already in `%APPDATA%\VectorCraft` are copied into it
+  (the originals stay), so someone updating a portable zip from before the marker keeps their
+  settings. If that folder isn't writable the app logs a warning and uses `%APPDATA%`. Deleting
+  `portable.txt` returns settings to the user profile (the `VectorCraftData` folder is left as it
+  is). The MSI has no marker. `VECTORCRAFT_CONFIG_DIR` still wins, `VECTORCRAFT_NO_PREFS` never
+  looks for the marker, and a portable copy skips the one-time read of the old DrawCraft settings.
+  The logic is in `apps/vectorcraft/src/profile.rs`. On the other platforms the marker goes where
+  the user sees the app, never inside it: on macOS next to `VectorCraft.app` (nothing is written
+  inside the signed bundle), for an AppImage next to the `.AppImage` file (`$APPIMAGE`; the mounted
+  executable's own folder is read-only). Flatpak isn't supported: `/app` is read-only and the
+  sandbox has no folder "beside the app", so a Flatpak install always uses its own config folder.
 - `vectorcraft.wxs` (WiX) is a per-machine install into Program Files with a Start Menu shortcut
   and an App Paths entry (Win+R `vectorcraft`). Same-version upgrades are allowed, so release
   candidates replace each other.
@@ -236,3 +243,4 @@ warning, never a failed build.
 |---|---|---|
 | 2026-10-14 | minor | RPM glibc floor names libm's `GLIBC_2.35`: RHEL 9's glibc 2.34 provides libc's through backports |
 | 2026-10-12 | minor | RPM dependencies use 64-bit runtime capabilities and enforce glibc 2.35 (#1275); real distro install/start-up checks remain pending |
+| 2026-10-12 | minor | Portable mode (#1366): the Windows portable zip ships `portable.txt`; where the marker goes on macOS and Linux, and what Flatpak can't do |

packaging/windows/portable.txt

@@ -3,7 +3,12 @@ VectorCraft portable mode
 While this file sits next to vectorcraft.exe, VectorCraft keeps its preferences, swatch and
 graphic style libraries, added fonts, crash-recovery files and logs in the VectorCraftData folder
 beside it, and writes nothing to %APPDATA%. Copy the whole folder to move VectorCraft with its
-settings.
+settings. The first time VectorCraftData is created, any settings already in
+%APPDATA%\VectorCraft are copied into it; the originals are left where they were.
+
+Keep this folder somewhere only you can write to: whoever can write here decides your settings,
+including the plug-ins and fonts folders VectorCraft loads from, and the Data Recovery copies of
+your unsaved documents are kept here too.
 
 Delete this file to use the normal per-user settings folder (%APPDATA%\VectorCraft) instead.
 If VectorCraftData can't be written (for example on a read-only drive), VectorCraft logs a