Bound extension job and window-alias state

Two service-worker leaks. Running jobs were only bounded by their watchdog, so
a command flood could hold many timers and results for up to JOB_TIMEOUT_MS;
cap concurrent jobs at 32 and reject beyond that, since a clear error beats an
unresponsive worker. Window aliases were never removed, so storage kept an
entry for every window the user had ever renamed.

Prune aliases against the live window set on list, rename, and close rather
than only on close, because windows also disappear without going through
windows.close.

Also extract the repeated job summary in perf.status into a helper.

extension/src/commands/windows.ts

@@ -14,9 +14,31 @@ export class WindowsCommands extends CommandGroup {
     "windows.open":   (a: WindowsOpenArgs) => this.windowsOpen(a),
   };
 
+  private async activeWindowIds(): Promise<Set<number>> {
+    const windows = await api.windows.getAll({});
+    return new Set(windows.map(w => w.id).filter(id => typeof id === "number"));
+  }
+
+  private async pruneAliases(activeIds?: Set<number>): Promise<Record<string, string>> {
+    const aliases = await getAliases();
+    const liveIds = activeIds || await this.activeWindowIds();
+    const pruned: Record<string, string> = {};
+    let changed = false;
+    for (const [id, alias] of Object.entries(aliases)) {
+      if (liveIds.has(Number(id))) {
+        pruned[id] = alias;
+      } else {
+        changed = true;
+      }
+    }
+    if (changed) await api.storage.local.set({ windowAliases: pruned });
+    return pruned;
+  }
+
   private async windowsList() {
     const windows = await api.windows.getAll({ populate: true });
-    const aliases = await getAliases();
+    const activeIds = new Set(windows.map(w => w.id).filter(id => typeof id === "number"));
+    const aliases = await this.pruneAliases(activeIds);
     return windows.map(w => ({
       id: w.id,
       alias: aliases[w.id] || null,
@@ -27,7 +49,7 @@ export class WindowsCommands extends CommandGroup {
   }
 
   private async windowsRename({ windowId, name }: WindowsRenameArgs) {
-    const aliases = await getAliases();
+    const aliases = await this.pruneAliases();
     aliases[windowId] = name;
     await api.storage.local.set({ windowAliases: aliases });
     return { windowId, name };
@@ -35,6 +57,11 @@ export class WindowsCommands extends CommandGroup {
 
   private async windowsClose({ windowId }: WindowsCloseArgs) {
     await api.windows.remove(windowId);
+    const aliases = await this.pruneAliases();
+    if (windowId in aliases) {
+      delete aliases[windowId];
+      await api.storage.local.set({ windowAliases: aliases });
+    }
     return { windowId };
   }