* fix(daemon): update existing worktree to latest remote on reuse
When an agent receives a new task on the same issue, the execution
environment is reused and the repo worktree already exists on disk.
Previously, `multica repo checkout` would fail because `git worktree add`
cannot create a path that already exists — so the agent worked on stale
code from the prior task.
Now `CreateWorktree` detects existing worktrees and updates them:
fetch origin, reset working tree, then checkout a new branch from the
latest remote default branch. The previous task's branch is preserved.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* fix(daemon): propagate actual branch name and use correct ref in worktree reuse
- Return (string, error) from updateExistingWorktree so collision-retried
branch name propagates to WorktreeResult
- Use baseRef directly instead of origin/baseRef — bare clone refspec maps
remote branches to local refs, so remote-tracking refs may not exist
- Remove redundant fetch (worktree shares object store with bare clone)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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