[build-tools] Stabilize remote simulator tunnels

[szdziedzic]

Why

Remote simulator jobs only polled the device-run session status while ngrok forwarding tasks and the agent-device, Argent, and serve-sim processes ran unsupervised. If one of those resources stopped, the already-published URL stayed visible but ngrok returned ERR_NGROK_3200 because its endpoint was offline. The detached-process helper also retained unbounded output.

How

• create one explicit ngrok session per device-run session and share it between its tool and serve-sim tunnels
• keep transient ngrok reconnects enabled, log disconnect/reconnect health, and fail after a 60-second disconnect grace period
• use joinable ngrok listeners so terminal forwarding failures are observable
• supervise the ngrok listeners and agent-device, Argent, and serve-sim processes while polling session status
• abort background status polling when a supervised resource fails
• cap detached process diagnostics at 256 KiB and include them in unexpected-exit errors
• attach device-run session metadata to ngrok sessions and endpoints for diagnosis

Test plan

• corepack yarn workspace @expo/build-tools jest-unit --runInBand src/steps/utils/__tests__/remoteDeviceRunSession.test.ts src/steps/functions/__tests__/startArgentRemoteSession-orchestration.test.ts (36 tests passed)
• corepack yarn workspace @expo/build-tools typecheck
• corepack yarn fmt:check
• oxlint on all six changed files
• full build-tools unit run: 1,015 tests passed; the remaining pre-existing environment-dependent tests could not access npm, macOS keychain services, or ps/pgrep in the sandbox

[github-actions]

✅ Thank you for adding the changelog entry!

[codecov]

Codecov Report

❌ Patch coverage is 73.98374% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.61%. Comparing base (0e85408) to head (3974d9d).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ld-tools/src/steps/utils/remoteDeviceRunSession.ts	75.43%	28 Missing and 1 partial ⚠️
...c/steps/functions/startAgentDeviceRemoteSession.ts	0.00%	2 Missing ⚠️
.../src/steps/functions/startServeSimRemoteSession.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4226      +/-   ##
==========================================
+ Coverage   63.54%   63.61%   +0.07%     
==========================================
  Files        1028     1028              
  Lines       47054    47167     +113     
  Branches     9891     9914      +23     
==========================================
+ Hits        29898    29999     +101     
- Misses      17055    17066      +11     
- Partials      101      102       +1     

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