test: raise vitest testTimeout to 30s

The 5s default failed three unrelated real-I/O tests on the CI Node-22 runner
in two days (dashboard optimize scan, codex resume differential, OTel DB
prune) purely from runner load. Hung tests still fail at 30s.

vitest.config.ts

@@ -6,5 +6,8 @@ export default defineConfig({
     // session-discovery env vars (CLAUDE_CONFIG_DIRS, HOME, XDG_*, every
     // provider-specific *_HOME) don't bleed real local data into fixtures.
     setupFiles: ['./tests/setup/env-isolation.ts'],
+    // Real-I/O tests (session parses, sqlite fixtures, worker pools) exceed the
+    // 5s default under CI runner load; a hung test still fails at 30s.
+    testTimeout: 30_000,
   },
 })