refactor(core): strengthen typing and normalize auth and model flows

Tighten executor, usage, model-resolution, and state-management
code with explicit types and safer record handling to reduce runtime
edge cases across providers.

Also normalize management-token failures to 403 responses, require API
keys consistently on cloud agent task routes with CORS-safe errors,
refresh stale Gemini CLI project IDs, prioritize Gemini search tools
correctly, add new provider/model registry entries, and serialize
integration tests for more reliable CI.

.github/workflows/ci.yml

@@ -436,7 +436,7 @@ jobs:
           cache: npm
       - run: npm ci
       - run: npm run check:node-runtime
-      - run: node --import tsx/esm --test --test-shard=${{ matrix.shard }}/2 tests/integration/*.test.ts
+      - run: node --import tsx/esm --test --test-force-exit --test-concurrency=1 --test-shard=${{ matrix.shard }}/2 tests/integration/*.test.ts
 
   test-security:
     name: Security Tests