🐛 fix: a rebased landing names its commit, and a landed task reads landed

[Misery7100]

Two engine defects from the 0.2 list. Both break an existing promise, so they ship as fixes rather than a design document.

1. A rebased landing names the commit that landed (lane.py). Source: a-rebased-landing-records-the-pre-rebase-commit, from bloomery T-0270.

• Cause: the runner writes the landing file at the attempt, naming the work commit. A rebase replays that file unchanged while giving the work commit a new sha, so the record named a commit no branch holds.
• Fix: after every rebase onto a moved base, in _land_rebased and _rebase_document, _restate_landings points each replayed landing file at its work commit's new sha, which is the parent of the commit that added the file. The rebased tip is then amended to carry the change. Fast-forward landings are untouched.
• Signing: the amend follows the host's git config, exactly as the rebase it follows does. It loses nothing the plain git rebase didn't already.

2. A landed candidate reads landed, not ready (projections.py, cli/manager.py).

• Cause: the state machine ends a candidate at ready and records its landing only beside it. So torve status and manager board showed landed tasks as ready, for days.
• Fix: a shared projections.landed_ids collects landed tasks from three sources: the board's landed_sha, the lane's landings, and landings shipped in the tree. status and manager board show landed for any ready task in that set, in text and JSON. _document_waits now uses the same helper.
• State machine: unchanged.
• JSON consumers: they now see landed as a state value.

Tests:

• Two new lane tests: a rebased landing names an ancestor of the tip, and a fast-forward landing is untouched.
• A new status test, and a board assertion added to an existing manager test.
• Full suite: 2261 passed. ruff, mypy and spec check are clean.

The third commit closes the source with "Fixed at 8b9d337". I'll correct that sha to the squash commit after merge, as with #4.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EabbhASMvWNhC7x4K9NJMF