fix(ci): refuse a committed .claude/settings.json in sandbox-lint

[potiuk]

Summary

• Why. Since feat(setup): ship the framework's agent settings as a template #1671 (Stop committing the framework's own .claude/settings.json; ship it as a template #1639), this repository's agent settings ship as tools/agent-isolation/claude-settings.template.json and .claude/settings.json is gitignored, so the sandbox-lint workflow stopped watching that path. A PR can still force-add the file; Claude Code would then load the committed copy for everyone who checks the repository out, and CI would never lint it, so it could weaken the sandbox around the linted template.
• What.
  • .claude/settings.json is back in the workflow's pull_request and push path filters.
  • A new step, Refuse a committed .claude/settings.json, fails while the file is tracked, and points the author at the template, the baseline and git rm --cached.
  • The .asf.yaml note on why the job is not a required check lists the path.

Type of change

• Skill change
• Tool / bridge contract
• Python package
• Groovy reference impl
• Cross-cutting
• Documentation
• Project template
• CI / dev loop (sandbox-lint workflow, .asf.yaml comment)

Test plan

• prek run --all-files passes
• The step's condition in a throwaway repository: passes with the file untracked, refuses once it is force-added

Notes for reviewers

• The job stays outside the required checks: it is path-filtered, and .asf.yaml explains why that cannot be required.
• Raised by a background security review of the feat(setup): ship the framework's agent settings as a template #1671 push.

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Gen-AI disclosure: prepared with the assistance of Claude Code (Claude Opus 5); reviewed by the author.

🤖 Generated with Claude Code