[eas-build-job] Add SSH build phase

[gwdp]

Why

First PR in the worker SSH stack (ENG-24547). An SSH session needs its own build phase so it shows up as a distinct step in the build logs and on the website instead of being folded into an unrelated phase.

How

Adds an SSH_SESSION entry to the BuildPhase enum, with its log display name and website id. No runtime behavior yet; later PRs in the stack use the phase.

Test Plan

Enum addition with no runtime behavior. CI passes.

[linear-code]

ENG-24547

[gwdp]

• [eas-cli] Add --ssh to workflow:run #4033
• [eas-cli] Add workflow:ssh command #4032
• [worker] Wire SSH session into build #4031
• [build-tools] Add worker-side SSH session helper #4030
• [eas-build-job] Add optional ssh field on job payloads #4083
• [eas-build-job] Add SSH build phase #4029 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.27%. Comparing base (379ed8f) to head (8297089).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4029      +/-   ##
==========================================
+ Coverage   62.27%   62.27%   +0.01%     
==========================================
  Files         994      994              
  Lines       44732    44733       +1     
  Branches     9412     9412              
==========================================
+ Hits        27851    27852       +1     
  Misses      15434    15434              
  Partials     1447     1447              

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[claude]

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[github-actions]

✅ Thank you for adding the changelog entry!