refactor: reuse pane resolver for watcher

[brickfrog]

Summary

• resolve pane watcher pane ids at watch/check time using the existing @tools.resolve_zellij_pane_id + list-panes JSON snapshot path
• remove the PR fix: revive pane watcher no-handoff watchdog #576 pane-id sidecar/diff producer flow from spawn/fork_wave/workspace helpers
• keep dump-screen polling, no-handoff stall emission, prod removal, and spawn launch diagnostics intact

Verification

• moon test --target native
• moon info --target native
• ! grep -rEn "pane_id_from_list_panes_diff|agent_pane_id_file_path|pane-ids/|spawn_diagnostics" src/
• ! grep -rEn "spawn_zellij_pane_viewport_subscribe|worker_no_handoff_prod_text" src/
• moon build src/bin/choir_lint --target native && _build/native/debug/build/src/bin/choir_lint/choir_lint.exe

Verification

Generated by Choir from commands executed in the leaf workspace.

• moon test --target native
  • exit: 0
  • head: 5b6f703
  • output tail:

Total tests: 2008, passed: 2008, failed: 0.

• moon build src/bin/choir_lint --target native && _build/native/debug/build/src/bin/choir_lint/choir_lint.exe
  • exit: 0
  • head: 5b6f703
  • output tail:

Finished. moon: no work to do

• ! grep -rEn "pane_id_from_list_panes_diff|agent_pane_id_file_path|pane-ids/|spawn_diagnostics" src/
  • exit: 0
  • head: 5b6f703