chore(testing): Phase 9 — bun:test suite + CI gating with no-DB fakes

Added a real test suite (32 tests, 0 external services) using bun:test with
in-process module mocking for @mcpedia/db, @mcpedia/queue, @mcpedia/core.

Enablers:
- apps/api: extracted createApp(deps?) factory + dashboard.ts module from
  index.ts so the HTTP surface is unit-testable (real queue is lazy-imported).
- packages/core: exported shouldCreateRevision pure predicate; restoreRevision
  gained an opts.reindex seam for the chunk-rebuild contract.
- apps/mcp: renamed smoke.test.ts -> smoke.ts (bun test now owns .test.ts),
  updated stale assertions (10 tools, 4 docs in docs section).
- infra: turbo test task (cache:false), test scripts across packages,
  @types/bun + tsconfig base types, CI 'Test' step after Build.

Packages with tests: embeddings(5), parser(5), search(8), core(4),
mcp(6 auth-gates), api(8 contracts).

All green: typecheck(4/4), test(6/6 pkgs), build(web). Live API verified
/health, /metrics, /dashboard, /hooks/* auth gate on temp port.

turbo.json

@@ -12,6 +12,9 @@
     "dev": {
       "cache": false,
       "persistent": true
+    },
+    "test": {
+      "cache": false
     }
   }
 }