test: add spread+flag axios mock helper to stop CI mock pollution

Bare `mock.module('axios', () => ({ default: { stubs } }))` is
process-global last-write-wins and drops `axios.create`, `request`,
`isAxiosError`, etc. that real consumers need. In CI's alphabetical
file order, that produces dozens of polluted failures (AgentsPlatformView,
schedule API, memory-stores API, etc.) that don't reproduce on WSL2.

Introduce `tests/mocks/axios.ts` with `setupAxiosMock()` — `require('axios')`
inside the factory, spread real shape, route each verb through a per-suite
`useStubs` flag. beforeAll flips on, afterAll flips off; the spread
fall-through eliminates cross-file leakage.

Refactored 12 axios mockers in tests/, plus the bare `@anthropic/ink` mocks
in ultrareviewCommand and onboarding suites (same pollution pattern broke
AgentsPlatformView's Box/Text rendering).

Verified: 5339/5345 tests pass locally; remaining 6 failures are
pre-existing isolation issues unrelated to this change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/builtin-tools/src/tools/WebSearchTool/__tests__/bingAdapter.test.ts

@@ -1,4 +1,12 @@
-import { describe, expect, mock, test } from 'bun:test'
+import { afterAll, describe, expect, mock, test } from 'bun:test'
+import { setupAxiosMock } from '../../../../../../tests/mocks/axios'
+
+// Each test below calls `mock.module('axios', ...)` per-test. Re-register a
+// spread-real axios mock at end-of-file so the per-test stubs do not leak
+// into subsequent test files (mock.module is process-global, last-write-wins).
+afterAll(() => {
+  setupAxiosMock()
+})
 
 const _abortMock = () => ({
   AbortError: class AbortError extends Error {