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

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 61.53846% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.93%. Comparing base (88a404e) to head (1fe93cb).

Files with missing lines	Patch %	Lines
...ld-tools/src/steps/utils/remoteDeviceRunSession.ts	66.67%	4 Missing ⚠️
.../src/steps/functions/startServeSimRemoteSession.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3885      +/-   ##
==========================================
+ Coverage   58.92%   58.93%   +0.02%     
==========================================
  Files         934      934              
  Lines       40835    40840       +5     
  Branches     8607     8607              
==========================================
+ Hits        24058    24066       +8     
+ Misses      16681    16678       -3     
  Partials       96       96              

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