Update development guidelines and improve icon update logic

- Enhanced icon update logic to simplify handling of tab activation
- Added cache check to skip events for removed queries in sync process

Author: dborysov

.github/agents/copilot-instructions.md

@@ -1,6 +1,6 @@
 # tanstack-query-chrome-devtools-3 Development Guidelines
 
-Auto-generated from all feature plans. Last updated: 2026-03-28
+Auto-generated from all feature plans. Last updated: 2026-03-30
 
 ## Active Technologies
 - TypeScript 5.9 (strict mode) + React 19, WXT 0.20, Tailwind CSS v4, lucide-react (for mutation status icons) (002-page-layout-placeholders)
@@ -40,6 +40,8 @@ Auto-generated from all feature plans. Last updated: 2026-03-28
 - N/A (no storage changes in this feature) (021-ui-layout-fixes)
 - TypeScript 5.9 (strict mode) + React 19, WXT (web extension framework), @tanstack/query-core (022-action-button-fetch-state)
 - N/A (in-memory state synced via message passing) (022-action-button-fetch-state)
+- TypeScript (strict mode) on React 19 + WXT + `@tanstack/query-core`, WXT, `lucide-react`, `highlight.js` (023-icon-stale-query-bugs)
+- N/A (ephemeral in-memory state + browser.storage.session for SW recovery) (023-icon-stale-query-bugs)
 
 - TypeScript 5.9 (strict mode) + React 19, WXT 0.20, Tailwind CSS v4, highlight.js 11, lucide-react, @tanstack/query-core (001-setup-connection-message)
 
@@ -59,9 +61,9 @@ npm test && npm run lint
 TypeScript 5.9 (strict mode): Follow standard conventions
 
 ## Recent Changes
+- 023-icon-stale-query-bugs: Added TypeScript (strict mode) on React 19 + WXT + `@tanstack/query-core`, WXT, `lucide-react`, `highlight.js`
 - 022-action-button-fetch-state: Added TypeScript 5.9 (strict mode) + React 19, WXT (web extension framework), @tanstack/query-core
 - 021-ui-layout-fixes: Added TypeScript (strict mode), React 19 + WXT (web extension framework), Tailwind CSS v4 (`@tailwindcss/vite`), `@tanstack/query-core`, `lucide-react`, `highlight.js`, `@tanstack/react-virtual` (to be removed)
-- 020-filter-relative-time: Added TypeScript (strict mode) + React 19.2 + React 19, @tanstack/react-virtual 3.13, WXT 0.20, Tailwind CSS v4
 
 
 <!-- MANUAL ADDITIONS START -->

entrypoints/background.ts

@@ -121,9 +121,7 @@ export default defineBackground(() => {
 
   // === Service worker recovery: restore icon on tab switch ===
   browser.tabs.onActivated.addListener(({ tabId }) => {
-    if (contentPorts.has(tabId)) {
-      updateIcon(tabId, "colored");
-    }
+    updateIcon(tabId, snapshotCache.has(tabId) ? "colored" : "gray");
   });
 
   // === Port connection handling ===

entrypoints/sync.content.ts

@@ -126,6 +126,12 @@ function startSync(client: NonNullable<Window["__TANSTACK_QUERY_CLIENT__"]>) {
       return;
     }
 
+    // Skip events for queries that have been removed from the cache
+    // (e.g., observerRemoved firing after removeQueries was called)
+    if (!queryCache.get(query.queryHash)) {
+      return;
+    }
+
     // added, updated, observerAdded, observerRemoved all map to entry updates
     const changeType = type === "added" ? "added" : "updated";
     postChange({