Proposal: Add git snapshot convention to AI-verified tests

What

Add a note below the AI-verified tests header that all AI tests run inside a git snapshot/restore cycle.

Why

AI tests may mutate the vault (create files, edit changelog, run skills). Without cleanup, fake data persists. Instead of per-test cleanup (error-prone), the runner always wraps all AI tests in git stash/restore.

Spec

Replace:

### AI-verified tests
| Scenario | Expected behavior | Verification method |
|----------|-------------------|---------------------|
| ...      | ...               | ...                 |

With:

### AI-verified tests
> Run inside git snapshot: `git stash -u` before, `git restore . && git clean -fd && git stash pop` after. Tests may freely mutate the repo.

| Scenario | Expected behavior | Verification method |
|----------|-------------------|---------------------|
| ...      | ...               | ...                 |

Impact

vault/_templates/feature-request.md only. Convention applies to all FRs using this template.