ci(release): move release-please off the shared-cache ARC pool (LAB-1040)

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LAB-1040 — shared persistent cargo cache on the ARC pool lets untrusted build scripts reach later credentialed jobs

release-please inherits the workflow-level contents: write + pull-requests: write and mints a GitHub App installation token, yet ran on the self-hosted cachekit ARC pool. That pool mounts a single hostPath /cache (CARGO_HOME, npm, pip, uv, go) shared across all pods and all cachekit-io repos — and job-level permissions: scopes tokens, not filesystems. A credential-less job compiling third-party crate code can poison /cache/cargo (a config.toml rustc-wrapper, a shimmed cargo-<subcommand> on PATH); the poison persists on the volume and executes later inside this credentialed job.

Change (option (a) from the ticket)

• release-please → runs-on: ubuntu-latest, with a comment stating the reason. It runs npm/action code only and opens a PR — no warm cargo cache needed. This matches all four sibling repos (cachekit-py, cachekit-ts, cachekit-rs, saas) and this file's own publish job.
• Two comments the move makes stale are corrected in the same diff: the "no gh CLI on the self-hosted runner" rationale (LAB-899) and the cargo-sbom --force persistent-CARGO_HOME rationale.
• No permissions change: still exactly one workflow-level permissions: block, and publish keeps its narrowing contents: read + id-token: write + attestations: write.

Post-merge verification (AC-4)

The release flow must be confirmed on a real run: after merge, the next push to main should open/update the release-please PR as usual. The App-token step and release-please-action are the parts most likely to behave differently on a hosted runner — please paste the run URL on the ticket.

Companion infra/docs PR in 27b-io/lab documents the pool's cache-sharing property and corrects ADR-0002's audit table (link on the ticket).

Summary by CodeRabbit

• Chores
  • Updated release automation to improve consistency and reliability across the publishing process.
  • Refined automation guidance and configuration to support broader execution environments.
  • Preserved existing package-generation and release-assignment behaviour.

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Walkthrough

The release workflow now runs release-please on ubuntu-latest. Comments document runner compatibility, cache isolation, credential permissions, and retained cargo-sbom installation behaviour.

Changes

Release workflow

Layer / File(s)	Summary
Hosted runner configuration and tool setup .github/workflows/release.yml	The release-please job uses ubuntu-latest. Comments document hosted-runner compatibility, cache isolation, credential permissions, and the retained forced installation of cargo-sbom.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 928fa

This localized workflow change is merge-ready after normal checks and review; no actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: moving the release-please job away from the shared-cache ARC pool.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch lab-1040-release-please-hosted

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Actionable comments posted: 1

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Inline comments:
In @.github/workflows/release.yml:
- Line 30: After the next push to main, verify that the release-please job on
ubuntu-latest completes successfully and that it opens or updates the release
PR, including confirmation that the App token permissions and
actions/github-script step work correctly.

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