fix: extension lifecycle leaks, image allowlist, generic image label

Audit fixes for the extension:

- Track and disconnect the changed::excluded-apps GSettings handler in
  disable() (it was the one connection whose id was never captured).
- Track the _stopDaemon 1.5s force-kill timer and cancel any leftover on
  enable(), so the source can't outlive a disable->enable cycle.
- Guard the exclusion-path delete with _proxy?.DeleteItemAsync.
- Mirror the daemon's image allowlist (drop avif/svg) in _pickMime.
- Show a generic "Image" label for all image rows instead of singling out
  PNG; the thumbnail identifies the image and the on-clipboard format (often
  PNG even for a copied GIF/WebP) is an implementation detail.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

strata@edu4rdshl.dev/extension.js

@@ -62,10 +62,16 @@ export default class StrataExtension extends Extension {
     enable() {
         this._shuttingDown = false;
         this._daemonRestartAttempts = 0;
+        // Cancel any pending force-kill timer left over from a previous disable
+        // (enable→disable→enable within 1.5s) so it can't outlive this cycle.
+        if (this._daemonKillTimerId) {
+            GLib.Source.remove(this._daemonKillTimerId);
+            this._daemonKillTimerId = null;
+        }
 
         this._settings = this.getSettings();
         this._excludedApps = this._settings.get_strv('excluded-apps');
-        this._settings.connect('changed::excluded-apps', () => {
+        this._excludedAppsChangedId = this._settings.connect('changed::excluded-apps', () => {
             this._excludedApps = this._settings.get_strv('excluded-apps');
         });
 
@@ -119,6 +125,10 @@ export default class StrataExtension extends Extension {
             for (const id of this._configChangedIds) this._settings.disconnect(id);
             this._configChangedIds = null;
         }
+        if (this._excludedAppsChangedId && this._settings) {
+            this._settings.disconnect(this._excludedAppsChangedId);
+            this._excludedAppsChangedId = null;
+        }
         this._panel?.destroy();
         this._panel = null;
         this._indicator?.destroy();
@@ -229,8 +239,7 @@ export default class StrataExtension extends Extension {
         const PREFERRED = [
             // Raster images (size-capped at MAX_IMAGE).
             'image/png', 'image/jpeg', 'image/jpg', 'image/gif', 'image/webp',
-            'image/bmp', 'image/tiff', 'image/avif', 'image/x-icon',
-            'image/svg+xml',
+            'image/bmp', 'image/tiff', 'image/x-icon',
             // Plain text (UTF-8 preferred, then locale, then X11 legacy aliases).
             // Ranked above rich-text so editors that expose both text/plain and
             // text/html give us raw source, not styled markup.
@@ -374,8 +383,10 @@ export default class StrataExtension extends Extension {
             // Graceful shutdown via D-Bus first.
             this._proxy?.ShutdownRemote(() => {});
         } catch (_) {}
-        // Give it 1.5s then force-terminate.
-        GLib.timeout_add(GLib.PRIORITY_LOW, 1500, () => {
+        // Give it 1.5s then force-terminate. Track the source so a re-enable
+        // within that window can cancel it (see enable()).
+        this._daemonKillTimerId = GLib.timeout_add(GLib.PRIORITY_LOW, 1500, () => {
+            this._daemonKillTimerId = null;
             try { daemonToStop.send_signal(15); } catch (_) {} // SIGTERM
             return GLib.SOURCE_REMOVE;
         });
@@ -532,7 +543,7 @@ export default class StrataExtension extends Extension {
             // Exclusion check - no clipboard I/O, just string comparison.
             if (this._isExcluded(this._currentFocusedApp)) {
                 try {
-                    await this._proxy.DeleteItemAsync(id);
+                    await this._proxy?.DeleteItemAsync(id);
                 } catch (e) {
                     // ignore - item may already be gone
                 }

strata@edu4rdshl.dev/ui/clipboardItem.js

@@ -224,7 +224,10 @@ export const ClipboardItem = GObject.registerClass({
         let subText  = '';
 
         if (mimeType.startsWith('image/')) {
-            mainText = mimeType === 'image/png' ? 'PNG image' : 'Image';
+            // Generic label - the thumbnail identifies the image, and the
+            // on-clipboard format (often PNG even for a copied GIF/WebP) is an
+            // implementation detail that misleads more than it informs.
+            mainText = 'Image';
         } else if (isUrl(preview)) {
             mainText = preview.trim();
             try {