Bootstrap and upgrade vibe-harness

vibe-harness is a kit of agent skills and governance templates. A repository adopts it by copying the kit's files in with its installer, which records every managed file in .agents/vibe-harness.lock.json. This skill fetches the kit and hands control to the kit's own BOOTSTRAP.md, which owns the full procedure for the version you fetched.

Fetch the kit

1. Find the kit repository: kit.repository in .agents/vibe-harness.lock.json when it exists, otherwise the URL the user gave, otherwise https://github.com/zehuichan/vibe-harness.

2. Clone it into a temporary directory outside the target repository; a partial clone keeps it small and still lets the installer fetch older files for three-way merges:

   git clone --filter=blob:none <kit-repository> <kit-dir>
   git -C <kit-dir> tag --sort=-v:refname
   git -C <kit-dir> checkout <newest tag, or the ref the user named>

   Reuse an existing clone only after git -C <kit-dir> fetch --tags origin. Use the default branch only when the kit has no tags or the user asks for it.

3. Read <kit-dir>/BOOTSTRAP.md and follow it from the section that matches the request: install, upgrade, changing the skill selection, status, or uninstall.

Rules that hold for every operation

• Run the installer with --dry-run first and show the user its plan before writing.
• Never edit files inside the kit clone; it is the upstream base for future merges.
• Exit code 2 means conflicts that need a decision. Report every one; never hide a conflict by deleting the lock file, overwriting a local edit, or passing --skip-conflicts without the user's agreement.
• Fill .agents/project-profile.md only with commands you ran successfully in this repository or facts you confirmed from its files.
• Do not commit, push, or open a pull request unless the user asks.