fix: preserve macOS clipboard shortcuts in text fields

[BIackFIame]

This independent first fix in a broader agent-workflow series restores native macOS editing in app fields and plugin pages; orchestration and routing changes will follow separately. Cmd+A/C/V now reach the focused field, while terminals and shortcut recorders retain the key events they need. Text also has a native editing context menu.

Validated at 22620f37: 1,802 tests passed, 3 skipped; helpers, typecheck, build and secret audit passed. Fork CI passed on macOS, Linux and Windows; that run restored the candidate tree under a temporary workflow overlay. A merge preview against upstream 6faadcdc is conflict-free, but the combined tree has not been rerun locally. Native clipboard dispatch in the visible app still needs a manual macOS check across a text field, plugin page, terminal and shortcut recorder.

Series order

1. macOS clipboard
2. Orchestration, reviews and budgets — Draft
3. Worktrees and checkpoints — Draft
4. Timeline, usage and attention — Draft
5. Network policies and temporary secrets — Draft
6. Workspace context and navigation — Draft
7. Experimental routing, handoff and remote controls — Draft

Parts 2–7 are cumulative Draft PRs against upstream main, with an isolated layer diff in each description. Their tested feature heads currently conflict with newer upstream changes; integration and fresh checks are required before readiness. Part 7 also retains its independent experimental acceptance gate.

[BIackFIame]

@codex review

Please review this PR for correctness, regressions and security issues. Review only; post findings on GitHub without changing code.

Current head: 22620f37238d4693c064216a5ba61fbc5fe7251d. Focus on native macOS editing, focus changes, plugin frames and shortcut recorders.