feat: consolidate web auth and add Effect v4 Project primitives

Auth:
- Add useWebAuth hook as the single web-facing auth interface with four
  states (loading/unauthenticated/authenticated/inconsistent)
- Normalize getCurrentUser to return {id: tokenIdentifier, name, email}
- Rename requireOwnerId to requireAuthUserId across all backend callers
- Set expectAuth:true on ConvexReactClient singleton
- Migrate _app, _auth, user-menu, use-personal-organization to useWebAuth
- Remove unused @code/auth/server export (zero callers confirmed)

Primitives:
- Add packages/primitives/src/project.ts with Effect v4 Project domain:
  URL normalization, six canonical context kinds, strict remote decoding,
  context write decisioning with revision tracking, and no-op detection
- Define PublicGit and ProjectStore replaceable ports
- Define ProjectApplication service orchestrating domain+ports with
  deterministic error mapping
- Add comprehensive test suite (28 tests) with in-memory store and fake
  PublicGit covering normalization, seeds, idempotency, tenant isolation,
  last-write-wins, and typed error mapping

packages/primitives/package.json

@@ -6,6 +6,7 @@
   "exports": {
     ".": "./src/index.ts",
     "./agent-os": "./src/agent-os.ts",
+    "./project": "./src/project.ts",
     "./signal": "./src/signal.ts"
   },
   "scripts": {