* fix(detect-changes): guard resolveWorktreeCwd against overriding a separately-indexed worktree
When the repo registry entry points to a linked worktree (both main
checkout and worktree indexed separately), resolveWorktreeCwd was
incorrectly replacing the correct worktree repoPath with the server's
main-checkout launch directory. Both share the same canonical root so
the existing same-repo check passed, causing git diff to run from the
wrong directory and return 0 changes (issue #1659).
Fix: early-exit guard — if tryRealpath(repoPath) differs from
tryRealpath(getCanonicalRepoRoot(repoPath)), repoPath is itself a
linked worktree and is returned unchanged. Auto-detection only fires
when repoPath equals the canonical main-checkout root.
Also normalises the launchCanonical comparison in the auto-detect path
to use tryRealpath for cross-platform consistency.
Regression test: 'returns worktreeDir unchanged when repoPath IS a
linked worktree and launchCwd is the main checkout'.
* test(detect-changes): add worktreeA→worktreeB case and assumption comment
Cover the missing case from the production-readiness review:
repoPath = wt-A (indexed), launchCwd = wt-B (server on a different
linked worktree). The guard fires on repoPath being a worktree
regardless of launchCwd, so wt-A is returned unchanged.
Also add an inline comment documenting the assumption that repoPath
is a git root or linked-worktree root (not an arbitrary subdirectory),
as noted in Finding 2 of the review.
* refactor(detect-changes): validate repoPath is a git root before canonical comparison
Instead of relying on a comment asserting repoPath is always a git
root, call getGitRoot(repoPath) first. Only if the result matches
repoPath itself do we call getCanonicalRepoRoot and apply the guard.
This eliminates the over-classification risk for subdirectory repoPath
values and makes the assumption explicit in code. repoCanonical is
shared across both the guard and the auto-detect block.
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Co-authored-by: Gergő Magyar <gergomagyar@icloud.com>
