Fix: set project-wide integration hookTimeout/testTimeout in vitest.config.ts

[AmaadMartin]

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Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• N/A — no existing issue; the change is described below.

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

Problem:

The integration project block in vitest.config.ts set no testTimeout or
hookTimeout, so every hook and test in that project inherited Vitest's defaults
(hookTimeout: 10000 ms, testTimeout: 5000 ms). Many integration tests are
install-heavy — their beforeAll runs npm install (and sometimes
npm run build) inside a fixture project, which routinely exceeds 10s on a
cold/loaded machine and flakes with Error: Hook timed out in 10000ms.
Individual files worked around this by inventing per-file timeout constants with
inconsistent values (20000 / 40000 / 60000), and the most exposed hook —
the beforeAll in tests/integration/build_setup/build_setup_test.ts, which
does both npm install and npm run build — passed no explicit timeout at all
and relied on the flaky 10s default.

Solution:

Add a named constant INTEGRATION_TIMEOUT_MS = 120000 and apply it as both
hookTimeout and testTimeout on the integration Vitest project block only.

• hookTimeout fixes the concrete npm install / npm run build hook flake.
• testTimeout gives a matching safe default to the test bodies. Explicit
  per-it() / per-hook timeouts still override it, so nothing regresses.
• 120000 sits comfortably above every existing per-file value
  (20000 / 40000 / 60000) and above the a2a server timeouts (60000).

The change is deliberately scoped to the integration project rather than the
top-level test block, so the fast unit:* projects keep quick failure
detection. It touches no test files. Per the repo style guideline ("Use named
constants for fixed values instead of hardcoding numbers"), the value is a
documented named constant rather than an inline literal.

Notes for reviewers:

• Coverage is N/A: this is a test-runner config-only change. Nothing under
  the coverage include globs (core/src, dev/src, integrations/src) is
  touched, so there are no new instrumented production lines to cover.
• Intentionally decoupled: follow-up cleanup of the now-redundant per-file
  TEST_EXECUTION_TIMEOUT constants is queued separately and must land after
  this change; the targeted build_setup_test.ts flake fix ships separately.
  This PR edits only vitest.config.ts to avoid coupling a shared-config change
  with those and to avoid merge conflicts.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

No unit test is added: the change is a static config literal in
vitest.config.ts, which is not part of the coverage-instrumented source set. A
bespoke test asserting on the raw config object would test Vitest's own config
plumbing, not ADK behavior, and is out of scope. As a regression guard, a
targeted unit run
(vitest run --project unit:core core/test/skills/skill_test.ts) passed with
unchanged fast-timeout behavior, confirming the unit:* projects are
unaffected.

Manual End-to-End (E2E) Tests:

Before/after proof that the new hookTimeout is actually in effect, run with no
mocks:

1. Create a scratch test under tests/integration/ whose beforeAll sleeps 11s
   (longer than the old 10s default) with no explicit per-hook timeout, then
   a trivial it(...).
2. npx vitest run --project integration <scratch_test> — passes at ~11s
   with this change; fails with Error: Hook timed out in 10000ms. when the
   change is reverted. (Verified both directions locally; the scratch test was
   not committed.)
3. Real install-heavy suite:
   npx vitest run --project integration tests/integration/build_setup/build_setup_test.ts
   — passes (20 passed, 4 skipped). This exercises the exact bare beforeAll
   (npm install plus npm run build per fixture) that was most exposed to the
   10s flake.

Tooling gates on the changed file: prettier --check vitest.config.ts (clean)
and eslint vitest.config.ts (clean) both pass; tsc --noEmit reports zero
errors on vitest.config.ts (the change adds no new type errors).

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

Additional context

This PR is config-only: the entire diff is 11 added lines in vitest.config.ts
(a documented INTEGRATION_TIMEOUT_MS constant plus the two fields on the
integration project block).