M15.2: merge main (disk cache, 3D Camera Tracker); camera analysis in workers; no disk cache on wasm32

The 3D Camera Tracker analysis joins the offloaded jobs. The disk cache stays off in the
browser (std::env::temp_dir panics on wasm32 once a config store exists).

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

crates/engine/src/session_settings.rs

@@ -27,6 +27,7 @@ impl Session {
         self.prefs.normalize();
         self.layer_cache.set_budget(self.prefs.layer_cache_bytes());
         self.footage.set_cache_budget(self.prefs.media_cache_bytes());
+        self.configure_disk_cache();
         // Fewer undo levels apply right away.
         let levels = self.prefs.general.undo_levels.max(1) as usize;
         if self.history.undo.len() > levels {
@@ -36,6 +37,43 @@ impl Session {
         self.prefs_revision += 1;
     }
 
+    /// Apply Settings ▸ Media & Disk Cache ▸ Disk Cache: open (or close) the persistent cache
+    /// and attach it to the layer cache. Without a folder setting the platform cache folder is
+    /// used, but only by frontends with a settings store (headless sessions stay off disk).
+    pub fn configure_disk_cache(&mut self) {
+        use effectcraft_render::disk_cache::{DiskCache, default_folder, footage_salt};
+        let d = &self.prefs.disk;
+        let folder = if d.disk_cache_folder.trim().is_empty() {
+            (self.config.is_some() && !cfg!(target_arch = "wasm32")).then(default_folder)
+        } else {
+            Some(std::path::PathBuf::from(d.disk_cache_folder.trim()))
+        };
+        let max = d.disk_cache_max_gb.max(1) as u64 * (1 << 30);
+        // (no file system in the browser: the disk cache stays off there)
+        let Some(folder) = folder.filter(|_| d.disk_cache_enabled && !cfg!(target_arch = "wasm32")) else {
+            self.disk_cache = None;
+            self.layer_cache.set_disk(None);
+            return;
+        };
+        let dc = match &self.disk_cache {
+            Some(c) if c.folder() == folder.as_path() => {
+                c.set_max_bytes(max);
+                c.clone()
+            }
+            _ => match DiskCache::open(&folder, max) {
+                Ok(c) => c,
+                Err(e) => {
+                    log::warn!("disk cache at {}: {e}", folder.display());
+                    self.disk_cache = None;
+                    self.layer_cache.set_disk(None);
+                    return;
+                }
+            },
+        };
+        self.layer_cache.set_disk(Some((dc.clone(), footage_salt(&self.project))));
+        self.disk_cache = Some(dc);
+    }
+
     /// Write settings to the config store.
     pub fn save_prefs(&self) {
         if let Some(c) = &self.config