fix: keep watcher arms and reply listeners alive through slow cycles …

[cloud-practitioner]

…(kunchenguid#6103)

• fix(bin): keep slow watcher cycles and preempted reply polls from breaking supervision

• fm_pending_reply_tick selects the records it has work for in one awk pass, so settled records cost no lock or fork and the walk no longer grows with the never-pruned store.
• An attached arm keeps following a live, identity-matched holder whose beacon went stale until the lock changes or the shared stall bound (fm_watcher_stall_bound), then fails with a typed stalled-holder line so the retry replaces the holder.
• The remote-reply adapter reports the job worker's preemption (exit 76) as a closed window, so the listener keeps its claim and polls again instead of being relaunched every watcher cycle.

• no-mistakes(document): Clarify watcher grace and attached-arm documentation