Worktree creation records: delete by id, audit rollbacks, and edge cases #356

Follow-ups to the worktree creation records (#344) in #349. Found by reading the code.

• The creation rollback (dispatch failure) and the removal path in apps/server/src/production/worktree_catalog_rpc.rs call delete_worktree_creation_record(path). A worktree recreated at that path in the gap loses its record. Delete by the id read when the worktree was resolved, as reap_worktree_creation_record does for the audit.
• Neither creation-rollback arm (record write failed, dispatch failed) calls worktree_audit::record_removal_outcome. The removal still happens but the profiler audit never sees it.
• reap_gone_records in apps/server/src/diagnostics/profiler/worktree_audit.rs treats NotFound as gone. A record on an unmounted volume is deleted although the folder still exists.
• A record can outlive its worktree if an unrelated folder is created at the same path later, which warns for that folder. A crash between Git's success and the record write leaves a worktree with no record.
• The tests for the .git pointer read pin the no-follow and non-blocking flags, not the ordering between the check and the open. The read is also not contained to a directory handle.