Aligns service-local vitest.config.ts with root config so tests pass
both via 'pnpm test' (uses service config) and 'npx vitest run' (uses root).
Fixes telemetry.test.ts which fails because its import chain eagerly
loads config.ts → envSchema.parse() requiring COSMOS_ENDPOINT/KEY/JWT_SECRET.
Added: RATE_LIMIT_STORE_MODE=memory, COSMOS_ENDPOINT, COSMOS_KEY, JWT_SECRET
(all test-safe placeholders, never used at runtime with DB_PROVIDER=memory)
- Add DB_PROVIDER=memory to vitest config for diagnostics tests
- Fix flaky timestamp comparison in 'should update a session' test
- Add 10ms delay between create and update
- Use toBeGreaterThanOrEqual instead of strict inequality
- All 17 diagnostics tests now pass
