Reject non-terminal ephemeral runner exits

[intel352]

Summary

• fail the provider job when run.sh --once exits while the matched GitHub workflow job is still non-terminal
• preserve workflow run/job ids in the proof for this failure mode
• add a regression test matching the STG symptom: GitHub job still in_progress, runner process exits cleanly

STG evidence

• v1.0.21 target workflow run 28454875323 assigned provider-target to ephemeral runner wfc-stg-ghp-linux-260629fabb6f-1509352a8137
• GitHub runner registration then reported that runner offline and busy while the target job remained in_progress
• STG workload controller run 28454768006 was cancelled as non-recoverable acceptance evidence

Verification

• GOWORK=off go test ./cmd/github-actions-runner-job ./internal -run 'EphemeralRunner|RunnerProvider|T915' -count=1
• GOWORK=off go test -race ./cmd/github-actions-runner-job -count=1
• GOWORK=off go test ./... -count=1
• GOWORK=off go build ./cmd/github-actions-runner-job
• git diff --check

[Copilot]

Pull request overview

This PR tightens the ephemeral GitHub Actions runner job driver so the provider job fails when run.sh --once exits cleanly while the matched GitHub workflow job is still non-terminal, and adds a regression test for the observed STG failure mode.

Changes:

• Detect and fail on clean runner exit when the matched GitHub job is still in_progress (non-terminal), while preserving run/job IDs in the result/proof artifact.
• Add a regression test covering “runner exits 0, GitHub job remains in_progress” and asserting proof includes workflow run/job IDs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
cmd/github-actions-runner-job/main.go	Adds a failure path when the runner exits before the observed GitHub job becomes terminal.
cmd/github-actions-runner-job/main_test.go	Adds a regression test that simulates the STG symptom and validates proof retention of run/job IDs.

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