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.

packages/core/src/index.service.ts

@@ -84,6 +84,22 @@ export async function indexContentFile(
   return { indexed: true, chunks, revision };
 }
 
+/**
+ * Pure decision rule for the revision system: create a new revision only when
+ * the body genuinely changed vs the latest snapshot.
+ * - no prior revision (latestBody null)  -> true  (first snapshot)
+ * - identical body                      -> false (no noise)
+ * - different body                      -> true
+ *
+ * Exported separately so it can be unit-tested without a database.
+ */
+export function shouldCreateRevision(
+  latestBody: string | null | undefined,
+  body: string,
+): boolean {
+  return latestBody == null || latestBody !== body;
+}
+
 /**
  * Compare the incoming body against the latest revision's body; if different
  * (or no prior revision exists), create a new revision with an incremented