The blob-sandbox feature (#243/#250) made AiChatToolsService.forUser()
eagerly call this.sandboxStore.asSink() while wiring the stash tool, but
the spec still passed an empty {} as the sandboxStore constructor arg.
That object has no asSink method, so all 19 tests in the suite failed in
CI with 'TypeError: this.sandboxStore.asSink is not a function'.
Replace the stale {} mock at all 4 constructor sites with a no-op sink
exposing asSink() -> { put, has, evict } (jest.fn()). These tests never
execute the stash tool, so a no-op sink is sufficient for forUser() to
wire successfully. Test-only change; production code is unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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