[KISS/SPoA] Decompose Win32MenuWindowTracker into hook, enumeration and policy components

[github-actions]

Audit finding

Win32MenuWindowTracker.cs contains the event args, public tracker interface, association policy, timer coordinator, WinEvent hook management, message-only window, menu-window enumeration, deduplication and native declarations.

As a result, a single class/file owns notification transport, candidate discovery, association policy and publication state.

Target state

Keep a small Win32MenuWindowTracker coordinator and extract focused collaborators:

• menu event hook/refresh signal source;
• menu-window enumerator;
• candidate/association policy;
• changed-window-set publisher or snapshot comparer.

Native declarations should move to the consolidated interop boundary tracked separately.

Acceptance criteria

• The tracker coordinates injected hook and enumeration ports.
• Candidate validation is pure and unit-testable without native windows.
• WinEvent/message-window behavior is isolated and disposable independently.
• Enumeration failure and hook failure policies remain explicit.
• Window-set deduplication has focused tests.
• The public tracker behavior and 75-ms fallback verification remain unchanged until the timing-policy issue is completed.