fix(setup): ignore the snapshot symlink that worktree-init creates

[potiuk]

Summary

• adopt writes /.apache-magpie/ and /.apache-magpie-sources/ into the adopter's .gitignore. A dir/-style pattern matches only directories — but only the main checkout has directories there. worktree-init deliberately replaces both with symlinks to the main checkout's copies so every worktree shares one framework state and picks up /magpie-setup upgrade automatically.
• Net effect: both entries show as untracked in every worktree of every adopter. That is git status noise on its own, and one careless git add -A away from committing a symlink whose target is a machine-local absolute path.
• Dropping the trailing slash matches the directory, its contents, and the symlink alike, so the main checkout is unaffected. verify check 4 is updated to expect the unslashed form and to flag a legacy /.apache-magpie/ entry as a finding.

Type of change

• Skill change (.claude/skills/<name>/) — eval fixtures updated below
• Tool / bridge contract (tools/<system>/*.md)
• Python package (tools/*/ with pyproject.toml)
• Groovy reference impl
• Cross-cutting (RFC, AGENTS.md, sandbox, privacy-LLM)
• Documentation (docs/, README.md, CONTRIBUTING.md)
• Project template (projects/_template/)
• CI / dev loop (prek, workflows, validators)
• Other:

Test plan

Verified the pattern semantics directly in a scratch repo, with /.apache-magpie as the only ignore line:

dir  -> IGNORED      # main checkout
file -> IGNORED      # .apache-magpie/skills/a.md
link -> IGNORED      # worktree symlink

and confirmed the old /.apache-magpie/ pattern reports the symlink as not ignored, reproducing the bug.

Also confirmed against a live adopter (apache/airflow, worktree off the main checkout): git status reported ?? .apache-magpie before, and is clean after.

• prek run --all-files passes — not run; the pre-commit hooks ran on the changed files at commit time and passed, including symlink-lint and skill-and-tool-validate
• For Python packages touched: n/a — no Python changed
• For Groovy bridges touched: n/a
• For skill changes: eval suite passes for the affected skill — n/a, see below
• For skill behaviour changes: a new or updated eval fixture is included in this PR — n/a, see below
• Other: no eval asserts the .gitignore entry list. grep -rn '^/\.apache-magpie/$' tools/skill-evals/evals/ returns nothing, and tools/skill-evals/evals/setup/ has no fixture mentioning gitignore, so there is no fixture to update and no existing eval this can regress. Happy to add a setup eval case pinning the entry list if you'd like the behaviour locked down.

RFC-AI-0004 compliance

• HITL — no new mutation
• Sandbox — no change to host access
• Vendor neutrality — the changed prose keeps the existing placeholders; no adopter-specific names introduced
• Conversational + correctable — no adopter-tunable behaviour added
• Write-access discipline — no outbound messages
• Privacy LLM — no content routed to an LLM

Linked issues

None filed — found while adopting the framework in apache/airflow. The adopter-side .gitignore entry there is being fixed separately; this PR fixes the source that generates it for every adopter.

Notes for reviewers (optional)

Two judgement calls worth a look:

1. /.claude/hooks/guards.d/ keeps its trailing slash. worktree-init copies the guards rather than symlinking them, so it is a real directory in every worktree and the slash is correct there. Only the two entries worktree-init symlinks are changed.
2. verify wording. I made the legacy slashed form an explicit ✗ rather than silently accepting both, and noted that the check has to run from a worktree to see the failure at all — in the main checkout the old pattern passes, which is exactly why this went unnoticed.