feat(web): add TanStack Query infrastructure (Phase 0)

- Install @tanstack/react-query v5 + devtools
- Create core/query-client.ts with WS-optimized defaults (staleTime: Infinity)
- Create QueryProvider and wire into root layout
- Add @core/* path alias to tsconfig + vitest
- Add useWorkspaceId() bridge hook for query key scoping

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/package.json

@@ -18,11 +18,12 @@
     "@dnd-kit/utilities": "^3.2.2",
     "@emoji-mart/data": "^1.2.1",
     "@floating-ui/dom": "^1.7.6",
+    "@tanstack/react-query": "^5.96.2",
+    "@tanstack/react-query-devtools": "^5.96.2",
     "@tiptap/extension-code-block-lowlight": "^3.22.1",
     "@tiptap/extension-image": "^3.22.1",
     "@tiptap/extension-link": "^3.22.1",
     "@tiptap/extension-mention": "^3.22.1",
-    "@tiptap/suggestion": "^3.22.1",
     "@tiptap/extension-placeholder": "^3.22.1",
     "@tiptap/extension-table": "^3.22.1",
     "@tiptap/extension-table-cell": "^3.22.1",
@@ -33,6 +34,7 @@
     "@tiptap/pm": "^3.22.1",
     "@tiptap/react": "^3.22.1",
     "@tiptap/starter-kit": "^3.22.1",
+    "@tiptap/suggestion": "^3.22.1",
     "@types/linkify-it": "^5.0.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",