fix: harden Window Layouts workflows

[xcv58]

Summary

Follow-up to #324 that applies the findings from a four-round review/fix loop to Window Layouts and its host integrations.

• keep queued commands bound to the intended window and make restored or cross-display windows reachable
• make custom-layout previews, shortcut errors, blank-name normalization, and preset assignment summaries match persisted behavior
• delete custom layouts and their shortcuts transactionally, restoring exact assignment records when either store fails
• preserve headless HUD feedback and invalidate Run Link safety immediately when custom action policy changes
• bound direct, indirect, and asynchronous shortcut retriggers without blocking normal rapid repeats

Compatibility and persistence

• preserve the released PluginKit v5 preset protocol ABI and move richer replacement behavior behind a new optional protocol
• require MacTools 1.2.1 for the new protocol and predeclare the host version accordingly
• report portable-preferences changes only after a successful changed shortcut transaction, never for no-ops or rollbacks
• extend the frozen PluginKit v5 client and minimum-host policy tests

Verification

• final two-stage fresh review: clean
• 87 repository script tests passed
• 59 focused host tests passed
• 76 Window Layouts tests passed
• PluginKit v5 binary compatibility client passed
• changelog validation and git diff --check passed
• post-rebase minimum-host and Debug manifest-copy tests passed (15 tests)