Use sjchmiela serve-sim previews without WebRTC

[sjchmiela]

Summary

• switch remote device run sessions to the serve-sim-sjchmiela preview helper
• report only the preview URL from serve-sim remote sessions
• avoid forcing WebRTC for tunneled previews for now, keeping the AVCC/H.264 path with MJPEG fallback

Why

The live WebRTC preview path can get stuck during /webrtc/offer while the helper waits for server-side ICE gathering, leaving the browser simulator surface at connecting. The AVCC and MJPEG stream endpoints are healthy in that state, so this keeps the new helper while avoiding the broken WebRTC signaling path.

Test plan

• yarn oxfmt --write packages/build-tools/src/steps/utils/remoteDeviceRunSession.ts packages/build-tools/src/steps/utils/__tests__/remoteDeviceRunSession.test.ts
• yarn --cwd packages/build-tools jest-unit src/steps/utils/__tests__/remoteDeviceRunSession.test.ts
• git diff --check main..HEAD

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.02%. Comparing base (88a404e) to head (604a714).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...ld-tools/src/steps/utils/remoteDeviceRunSession.ts	71.43%	4 Missing ⚠️
.../src/steps/functions/startServeSimRemoteSession.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3885      +/-   ##
==========================================
+ Coverage   58.92%   59.02%   +0.11%     
==========================================
  Files         934      935       +1     
  Lines       40835    40941     +106     
  Branches     8607     8625      +18     
==========================================
+ Hits        24058    24163     +105     
- Misses      16681    16682       +1     
  Partials       96       96              

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[github-actions]

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