Restore green type-check baseline (117 tests + tsc all pass)

Fixes 3 pre-existing TypeScript errors that vitest did not catch but
tsc --noEmit did:
- apps/mcp-linkedin/src/tools.test.ts: spread TOOL_NAMES before .sort()
  (readonly tuple has no mutating sort)
- packages/sanitize/src/corpus.test.ts: cast through unknown to FixtureMeta
- db/migrations/rehearse.ts: add 'postgres' driver dependency (also needed
  to run the migration itself)

Also: apps/admin test script uses --passWithNoTests (Stage 5 admin app has
no test files yet, vitest exited non-zero on empty).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/mcp-linkedin/src/tools.test.ts

@@ -4,7 +4,7 @@ import { outletForAuthorUrn, validateToolCall } from "./server";
 
 describe("Tool registry — 9 tools per Plan §3.2", () => {
   it("exposes exactly the 9 tools named in the plan", () => {
-    expect(TOOL_NAMES.sort()).toEqual(
+    expect([...TOOL_NAMES].sort()).toEqual(
       [
         "linkedin_whoami",
         "linkedin_auth_status",