After merge:reuse-handoff-refused with no usable task worktree:
- Acquire a fresh worktree and restore the fusion/<task-id> branch
from baseCommitSha before continuing merge
- Hard-fail only if fresh acquisition itself fails (not cwd-main fallback)
- Emit merge:reuse-worktree-fresh-acquire / merge:reuse-worktree-fresh-acquired
audit events around the acquisition lifecycle
Replaces the incorrect cwd-main fallback (499784581) with correct
reacquire path. Updates regression test in merge-reuse-task-worktree.test.ts
to assert fresh-acquire audit trail instead of cwd-main fallback.
Refs: FN-5353
6d66559eb3