🤖 fix: isolate workflow action exec diagnostics

[ThomasK33]

Summary

Fix workflow action diagnostics so output produced by ctx.exec commands stays on the returned command result instead of being echoed into the action-level stdout/stderr fields. Also suppress stderr from the internal ps cleanup probe so host warnings do not pollute action diagnostics.

Background

A workflow run showed built-in Git actions with confusing action diagnostics: stdout contained concatenated internal Git command output and stderr contained host ps warnings such as bad data in /proc/uptime. The structured output fields were usable, but the action-level diagnostics were misleading.

Implementation

• Stop forwarding ctx.exec child stdout/stderr chunks to the action child process stdout/stderr while still draining and returning those streams from ctx.exec.
• Run the cleanup ps probe with stderr ignored.
• Add regression coverage for command-output isolation and deterministic fake-ps cleanup warning suppression.
• Keep the Git action workflow regression assertions that distinguish git.diff patch output from git.diffStat stat output.

Deep Review

Ran deep-review-workflow after the initial commit. It identified two actionable findings, both addressed:

• Added deterministic coverage for noisy cleanup ps stderr.
• Removed the accidental duplicate scratch workflow .gitignore block.

Workflow run: wfr_4254a7721b3f70f4.

Validation

• bun test src/node/services/workflows/WorkflowActionRunner.test.ts --timeout 30000 --test-name-pattern "cleanup ps warnings|ctx.exec output"
• bun test src/node/services/workflows/WorkflowRunner.test.ts --timeout 30000 --test-name-pattern "runs built-in Git workflow actions"
• Isolated git check-ignore -v --no-index check for .mux/workflows/.scratch/.gitignore vs a scratch draft file
• git diff --check origin/main..HEAD && git diff --check
• make static-check

Risks

Low-to-medium. The production change affects workflow action diagnostics only: command streams are still drained to avoid backpressure and still returned through ctx.exec. Users who depended on implicit live echoing from ctx.exec into action stdout/stderr would no longer see those chunks there; actions can still log explicitly with console.log when desired.

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Generated with mux • Model: openai:gpt-5.5 • Thinking: xhigh • Cost: 702472{MUX_COSTS_USD:-0}

[ThomasK33]

@codex review

Please review the workflow action diagnostics fix.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Nice work!

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