[build-tools] Stop agent-device artifact polling before daemon shutdown

[szdziedzic]

Why

Follow-up to #4114.

The agent-device artifact poller was launched as a detached, unconditional loop. Once the remote session ended, teardown stopped the daemon but the poller kept requesting its artifact endpoint forever, producing repeated failures and periodic Sentry reports.

How

• Give the artifact poller a required abort signal and propagate it to the daemon inventory request.
• Make the five-second polling delay abortable.
• Combine the build-step signal with a dedicated lifecycle controller.
• Abort and await polling before stopping the daemon.
• Keep daemon cleanup in a nested finally so an earlier preview or tunnel cleanup failure cannot leave the poller and daemon running.
• Report unexpected polling shutdown failures without skipping daemon shutdown.

Test Plan

• corepack yarn test src/steps/utils/__tests__/agentDeviceArtifacts.test.ts src/steps/functions/__tests__/startAgentDeviceRemoteSession.test.ts --runInBand (11 tests)
• corepack yarn typecheck in packages/build-tools
• Type-aware Oxlint on all modified files
• Oxfmt check on all modified files

[github-actions]

✅ Thank you for adding the changelog entry!

[codecov]

Codecov Report

❌ Patch coverage is 58.82353% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.25%. Comparing base (f145ed7) to head (9a61baf).

Files with missing lines	Patch %	Lines
...c/steps/functions/startAgentDeviceRemoteSession.ts	45.46%	10 Missing and 2 partials ⚠️
...uild-tools/src/steps/utils/agentDeviceArtifacts.ts	83.34%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4115      +/-   ##
==========================================
+ Coverage   62.25%   62.25%   +0.01%     
==========================================
  Files         994      994              
  Lines       44820    44843      +23     
  Branches     9425     9431       +6     
==========================================
+ Hits        27897    27913      +16     
- Misses      15474    15481       +7     
  Partials     1449     1449              

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