[build-tools] Share remote session teardown across the automation steps

[vonovak]

Why

The Agent Device, Appium and Argent steps each had their own teardown. When teardown failed, its error replaced the error that had ended the session, in all three steps.

How

finishRemoteSessionAsync runs every teardown, logs each failure, and rethrows the first one only when the session itself succeeded. All three steps use it.

Each step hands it independent entries: the tunnel close, the collector stop with the process stop in a finally, and the host finish. Before, one entry ran them in sequence, so a rejected Appium collector stop left the Appium process running.

Stack 4/6, based on #4430, followed by #4435 → #4441.

Test plan

The orchestration tests fail teardown while the session body fails at each phase and assert the body error reaches the caller. Each case failed before this change. A new case rejects the collector stop and asserts the process stop and host finish still run; it failed for Appium before the change.

🤖 Generated with Claude Code

https://claude.ai/code/session_01D29AEWN9ajZXbzobHUH4fF

[codecov]

Codecov Report

❌ Patch coverage is 92.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.42%. Comparing base (30d558b) to head (e780c40).

Files with missing lines	Patch %	Lines
...ls/src/steps/functions/startArgentRemoteSession.ts	78.58%	3 Missing ⚠️

Additional details and impacted files

@@                         Coverage Diff                          @@
##           codex/session-host-finish-policy    #4431      +/-   ##
====================================================================
+ Coverage                             72.42%   72.42%   +0.01%     
====================================================================
  Files                                   973      973              
  Lines                                 46363    46369       +6     
  Branches                               9956     9953       -3     
====================================================================
+ Hits                                  33574    33580       +6     
  Misses                                11794    11794              
  Partials                                995      995              

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[github-actions]

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