refactor(app): own optional first-run setup admission

[jbeckwith-oai]

Move optional first-run shell setup admission and its existing tests from pkg/custom to internal/app, alongside the invocation that owns it. Update the caller directly; no compatibility wrapper or new abstraction.

Production implementation is identical except for its package declaration. Terminal eligibility, synchronous audio command traversal, argument copying, the single-worker gate, and the 250 ms foreground wait remain unchanged. Image shell installation mechanics stay in the image feature. Scanner test fixtures register the same audio commands directly with unused presentation callbacks omitted.

Validation: go test -race ./internal/app -count=1, go test ./... -run '^$', Windows amd64 app compilation, and go vet ./internal/app passed. The existing production-guard PTY test also passed with all standard streams attached. Basic diff review and whitespace checks passed. Generated sources, dependencies, and budget policy are unchanged.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-20T02:19:34.060162Z	f8588dc	PR opened
🔒 Security Review	✅ Completed 2026-10-20T02:20:44.385060Z	f8588dc	PR opened

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[github-actions]

Castiron custom code

Evaluated main: 7e8300adcef5ccabe13574f9c818401147ff9686.

Trusted main policy: 7e8300adcef5ccabe13574f9c818401147ff9686.

✅ No new custom-code files detected.

0 mixed files remain; 0 existing customizations changed.

Compared 7e8300adcef5 → f8588dcd87a4. Generated baselines verified.

A changed generated baseline means this report cannot reliably identify which handwritten lines changed.

Inspect the custom-code diff

Download the exact patch produced by this run (requires repository access):

gh run download 39358217324 --repo openai/openai-cli \
  --name castiron-custom-code-39358217324-1 --dir /tmp/castiron-custom-code-39358217324-1
git apply --stat /tmp/castiron-custom-code-39358217324-1/custom-code.patch
cat /tmp/castiron-custom-code-39358217324-1/custom-code.patch

Or reproduce it from an SDK checkout containing the vendored reporter:

git fetch --no-tags origin 7e8300adcef5ccabe13574f9c818401147ff9686 f8588dcd87a499da564039a5d85b8937b2a81fde
python3 scripts/castiron/custom_code_report.py report \
  --base 7e8300adcef5ccabe13574f9c818401147ff9686 \
  --head f8588dcd87a499da564039a5d85b8937b2a81fde --fetch --require-head-hash --public \
  --out /tmp/castiron-custom-code-f8588dcd87a4
cat /tmp/castiron-custom-code-f8588dcd87a4/custom-code.patch

This is the current full custom patch for mixed files, not an attribution of only the handwritten lines changed by this PR.

Full report and patch