fix(projects): keep worktrees when unreachable [2]

[AbysmalBiscuit]

A transient wsl.exe failure silently collapses a WSL project's worktree list to a single pseudo-worktree. Project::discover now reports whether its answer is authoritative, and callers adopt through Project::apply, which drops a result the backend could not vouch for.

The bug

discover_wsl returned Project::placeholder on a failed round trip — the same single pseudo-worktree a non-git folder gets. Both Project::refresh and AlacritreeApp::poll_project_refreshes copied that straight over worktrees and default_branch, so one flaky round trip was indistinguishable from "every worktree in this project was deleted". The sidebar collapsed to one row and stayed that way until a later refresh happened to succeed.

Same failure shape as 17f95c23 fix(wsl): keep last probe when helper is briefly down, which fixed the foreground-TUI probe cache: a transport error collapsing into the same value as a definitive negative answer.

The change

• Project::discover returns Discovered { project, authoritative }.
• classify_wsl_answer(reached, is_repo, worktrees_parsed) -> WslAnswer is a pure function, so all three outcomes are reachable in a test without a WSL host. discover_wsl classifies once at the end rather than returning early three times.
• Project::apply adopts a result, ignoring a non-authoritative one. expanded, shell_override, and label remain untouched either way, as before.
• Callers in app.rs and cli/offline.rs take .project; the background refresh channel carries Discovered.

A distro that answers "this is not a repository" is still authoritative — that is the truth, and the placeholder is correct. Only a round trip that never landed, or one that came back claiming a repo with no main checkout, is treated as unknown.

Testing

Four new tests in projects::tests. They failed to compile first, then the finished code was hotpatched to drop the if !found.authoritative { return; } guard, reproducing the bug:

assertion `left == right` failed
  left: 1
 right: 2

Guard restored, green. Full suite: 480 passed. cargo clippy -p alacritree --all-targets warning count unchanged from master, none in the touched files.

Still to verify manually: add a project on a WSL path, break wsl.exe on PATH, force a refresh, and confirm the worktree list survives.

🤖 Generated with Claude Code