[eas-build-job] add DeviceRunSession.Job

[szdziedzic]

Why

EAS Simulator sessions (device run sessions) currently reach the worker as a Generic.Job with a hand-built list of eas/* steps. The steps engine runs strictly in sequence, so the build download, tool installs, and TURN credential fetch all wait for the simulator boot, and ordering rules such as "capture must start before the app launches" live only in the API server's step lists. See the discussion in expo/universe#30577.

This is the first PR of a stack that gives sessions a typed job payload and a worker-owned lifecycle:

1. [eas-build-job] add DeviceRunSession.Job #4412 (this PR) [eas-build-job] the DeviceRunSession.Job payload
2. [build-tools] add device run session runner #4413 [build-tools] the session runner
3. [worker] run device run session jobs #4414 [worker] dispatch

How

• Adds DeviceRunSession.Job (packages/eas-build-job/src/deviceRunSessionJob.ts): a Zod schema describing the session (controller, duration, idle timeout, tunnel domain), the device (iOS or Android, discriminated on platform), the optional application to install and launch, and the optional local egress.
• type: 'device-run-session' is the job-family discriminator. Generic.JobZ already reserves platform and type as never for this purpose; build jobs use type for their Workflow, generic jobs leave it undefined, and session jobs set this literal. The comment in generic.ts now names all three families.
• Exports Generic.BuilderEnvironmentSchemaZ so the new schema reuses it, and exports the StaticWorkflowInterpolationContext type.
• This PR does not add the new job to the Job union yet; [build-tools] add device run session runner #4413 does that together with the code that handles it.

Test Plan

• New schema tests: valid iOS and Android payloads round-trip, and the schema rejects local egress on Android, an idle timeout that is not shorter than the duration, two application sources, a build-job type, a set platform, and an empty session id.
• yarn typecheck, yarn lint, yarn fmt:check, and cd packages/eas-build-job && yarn test pass.

🤖 Generated with Claude Code

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.21%. Comparing base (97007d1) to head (37c3973).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4412      +/-   ##
==========================================
+ Coverage   72.19%   72.21%   +0.02%     
==========================================
  Files         970      971       +1     
  Lines       46046    46071      +25     
  Branches     9875     9882       +7     
==========================================
+ Hits        33240    33265      +25     
  Misses      11811    11811              
  Partials      995      995              

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