Fix: pin the test log level inside the vitest workers, not in globalSetup

[AmaadMartin]

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Link to Issue or Description of Change

1. Link to an existing issue (if applicable):
   Closes: #issue_number
   Related: #issue_number

No tracking issue. The ineffective pin this PR repairs was introduced in google#120 ("chore: mute @google/adk logs while running tests").

2. Or, if no issue exists, describe the change:

Problem: tests/global_setup.ts calls setLogLevel(LogLevel.ERROR) to mute @google/adk logs during the test suite. It never worked. A vitest globalSetup module runs once, in the Vitest main process, while every test file runs in a separate forked worker (default pool forks, isolate: true). The level is module-level state — setLogLevel mutates currentLogger (core/src/utils/logger.ts:119), whose SimpleLogger holds private logLevel = LogLevel.INFO (core/src/utils/logger.ts:35). Module state does not survive the fork, so each worker started fresh at INFO and the call mutated a logger no test ever used. teardown() was dead for the same reason.

Measured on core/test/plugins before the fix: 10 INFO: [ADK] ... lines of noise (e.g. Plugin 'plugin1' registered.).

A second symptom: because globalSetup runs in the main process, the project alias does not apply to it, so on an unbuilt tree the file aborted the entire run with Failed to resolve entry for package "@google/adk".

Solution: Move the pin into a per-project setupFiles module, which vitest evaluates inside each worker before the test file. tests/global_setup.ts is deleted and globalSetup removed.

• Why not root-level setupFiles: Vitest 3.2 inline projects entries do not inherit root test options, so a root-level entry simply never runs.
• Why not extends: true: it would change inheritance for every root option at once (coverage, poolOptions, include) — too large a blast radius for a bug fix, and no smaller (still six added lines).
• Why the entry is repeated six times: that is this file's existing convention; the 4-line alias block is already repeated six times. Hoisting it into a shared constant was deliberately left alone because a separate open PR already owns that refactor.
• Why the setup file imports ../core/src/utils/logger.js and not @google/adk: this is the one non-obvious part. A setup file is evaluated before the test module, so importing the public barrel there instantiates the real core module graph before a test file's hoisted vi.mock calls can replace any of it. Measured: with the barrel import, 103 test files / 110 tests failed (unmocked Runner, unmocked express, real UUIDs instead of mock-uuid). Importing only the logger module pulls in logger.ts + winston and nothing else, and the whole suite passes. The comment in the file records this so the "cleanup" to a barrel import is not made later.

No file under core/src/, dev/src/ or integrations/src/ is touched; there is no public API change and the shipped packages are unaffected. Only the test harness changes.

Collision check (required before implementation): gh pr list --repo AmaadMartin/adk-js --state open --limit 100 plus gh pr diff --name-only on every vitest-adjacent PR (#343, #341, #324, #311, #302, #281, #261). No PR lands this change. One genuinely overlaps: #302 fix/hermetic-unit-test-env adds setupFiles to the same three unit project entries. Two independent setupFiles: keys added to the same object literal would merge into a duplicate key and break the config, so this PR is stacked on fix/hermetic-unit-test-env rather than branched from main, and extends its array instead of adding a second key. Its base must stay that branch until #302 merges.

Testing Plan

Please describe the tests that you ran to verify your changes. This is required for all PRs that are not small documentation or typo fixes.

Unit Tests:
[x] I have added or updated unit tests for my change.
[x] All unit tests pass locally.

Added one new file, core/test/utils/log_level_pin_test.ts (project unit:core, which CI runs). No existing test was modified or deleted. SimpleLogger.logLevel is private and there is no read accessor, and reaching in with getLogger()['logLevel'] is not acceptable, so the test observes the level the only public way — by capturing what the logger writes. Winston's Console transport writes to the stream held by whatever globalThis.console is at log time, so the helper swaps in a node:console Console bound to an in-memory Writable; vi.spyOn(process.stdout, 'write') and vi.spyOn(console, 'log') capture nothing here because vitest replaces the global console with its own instance backed by a private stream.

Proof each test can fail (both mutations run against the final code):

1. Pre-fix baseline. The test file was written and run before vitest.config.ts was touched. suppresses info logs failed verbatim:

   AssertionError: expected '\u001b[32mINFO\u001b[39m: [ADK] 2026-…' to be '' // Object.is equality
   
   - Expected
   + Received
   
   + INFO: [ADK] 2026-07-30T23:40:22.034Z info-pin-probe
   

   still emits error logs passed, proving the capture harness itself works and the toBe('') assertion is not vacuous.

2. Mutation A — delete the setupFiles entry from the unit:core project only. suppresses info logs FAILS with the same AssertionError above; still emits error logs passes. Restored.

3. Mutation B — over-mute: replace the pin with setLogger(null). still emits error logs FAILS with AssertionError: expected '' to contain 'error-pin-probe'; suppresses info logs passes. Restored. This is the control that stops a future "fix" from silencing errors too.

Regression gate. Because this change alters the environment of every test file, the two unit projects CI gates on were run in full and compared against the branch point:

	Test files	Tests
Base (fix/hermetic-unit-test-env)	175 passed (175)	2414 passed (2414)
With this change	176 passed (176)	2416 passed (2416)

Exactly the one new file and its two tests; nothing else moved.

Noise actually gone. npx vitest run --project unit:core core/test/plugins: [ADK] lines drop from 11 (10 INFO + 1 ERROR) to 1 (the ERROR). The ERROR line is retained by design.

CI is absent on this PR, so it was validated locally instead. .github/workflows/validation.yaml triggers on pull_request: branches: [main], and this PR targets fix/hermetic-unit-test-env (see the stacking note above), so run-tests never fires — only the trivial auto-assign check appears, which is not validation. Everything below was therefore run locally against the exact pushed commit 4abddd7 with a clean working tree:

npm run build          # exit 0
npm run lint           # exit 0
npm run format:check   # exit 0
npx secretlint "**/*"  # exit 0
npm run docs:check     # exit 0
npx vitest run --project unit:core --project unit:dev   # exit 0 -- 176 files, 2416 tests

Other checks, all on the pushed commit:

• npm run lint — pass (exit 0). npm run format:check — pass. npx secretlint "**/*" — pass. npm run build — pass.
• npm run ts:check — 308 errors, but the error sets are byte-identical with and without this change and none are in the touched files (CI does not run ts:check).
• unit:integrations — 1 failure, integrations/test/version_test.ts (expected '1.4.0' to be '1.3.0'), identical with and without this change; a pre-existing rotted version pin already covered by another open PR.
• integration project — fails on both base and this branch with Hook timed out in the fixture npm install/bundling hooks (build_setup, agent_loader, app_loader, skills/script_js), a known pre-existing flake in this environment. Confirmed non-causal: run three times in each configuration, base flaked too (1/3 failures), and vitest reports this change's setup cost as 142ms against a 40,000ms hook budget.
• e2e and cross-language were not run locally — they require credentials. Both still receive the same setupFiles entry.

Manual End-to-End (E2E) Tests:
Please provide instructions on how to manually test your changes, including any necessary setup or configuration.

npm install && npm run build

# 1. The regression test passes.
npx vitest run --project unit:core core/test/utils/log_level_pin_test.ts

# 2. The INFO noise is gone; the ERROR line remains.
npx vitest run --project unit:core core/test/plugins 2>&1 | grep '\[ADK\]'

# 3. Revert the fix to see the bug: drop the './tests/setup_log_level.ts'
#    entry from the unit:core project in vitest.config.ts and re-run step 1.
#    'suppresses info logs' fails and step 2 prints 10 INFO lines again.

# 4. Full gate.
npx vitest run --project unit:core --project unit:dev

Checklist

[x] I have read the CONTRIBUTING.md document.
[x] I have performed a self-review of my own code.
[x] I have commented my code, particularly in hard-to-understand areas.
[x] I have added tests that prove my fix is effective or that my feature works.
[x] New and existing unit tests pass locally with my changes.