test(hook-augment): pin worktree payload-cwd resolution

[bmcnaboe]

Regression tests for the hook augment payload-cwd -> project resolution across a linked git worktree, on a real worktree fixture:

• payload cwd inside an indexed linked worktree (and a subdir) resolves to that worktree own project, never a sibling checkout or nothing;
• an unindexed worktree gets a deliberate "no indexed graph project matched" notice, never a silent 0 bytes;
• main-checkout resolution is unchanged.

Current main already resolves worktrees correctly; this adds the coverage that was missing so it cannot regress. Opened as a draft.

Fixes #1752

[github-actions]

Thanks for opening this — it has been seen, and it is queued.

This note is automated, but it is not a brush-off: it exists so you know where your PR stands instead of having to guess from silence.

Current review status: working through a backlog. 0.9.1-rc.1 is out, so the release freeze that held reviews is over — but it left a large queue of open pull requests behind it, and we are reading through them oldest-first. The background is in discussion #1144.

What that means for this PR, concretely:

• It will not be closed for inactivity. No stale bot touches pull requests here.
• It may still sit a while before a human reads it. That is on us, not on you.
• Older PRs are read first, so a recent one is not being skipped — it is behind a queue.

Things that will genuinely speed it up whenever review does happen:

• Keep it rebased on main — the tree is moving quickly right now, and a conflicting branch cannot be reviewed as the diff you intended.
• Get CI green, or say which failures you believe are pre-existing.
• Keep the change to one claim. Bundled features and refactors get split before they get merged, which costs you a round trip.
• Every commit needs a sign-off (git commit -s) — CI enforces DCO.

If this fixes a bug, a reproduction we can run is worth more than a description of the symptom.

Thanks for contributing, and sorry in advance for the wait.