Correct Windows toolbar destinations and scoped keyboard focus

[coneilen]

Summary

Correct destination-specific toolbar behavior and add explicit, scoped keyboard focus. Both affected parity-ledger rows remain Partial.

Changes

• Share header visibility and layout across rendering, hit-testing, UIA exposure, and focus order.
• Preserve visible workspace/project identity without overpainting toolbar controls.
• Keep loop-detail toggling inside the workspace rather than navigating back to the project.
• Open the selected needs-you target and gate cached worktree notices by matching local owner and count/size threshold.
• Preserve the existing Jump palette and allow it to open with no projects.
• Add View-menu-discoverable F6 toolbar entry/exit, scoped traversal/activation, focus rendering, and UIA Button semantics.
• Preserve ordinary Tab/Shift+Tab loop navigation, Ctrl+Tab attention selection, and modifier/menu/modal exclusions.
• Add production-helper tests, actual hidden-HWND Tab accelerator coverage, and a hidden native empty-palette test.

The only shared test-script change adds the required -lgdi32 linkage to the existing JumpPalette test invocation. No live module, shared-gate integration, or provider-pin changes are included.

Evidence

RED: Restore the generic panel transition and inspection-presence-only visibility in production helpers -> tests fail with expected workspace/found project and at the below-threshold worktree-notice assertion.
GREEN: Restore the reviewed helpers and rerun identical tests -> both pass, with pre-mutation source hashes restored.
REGRESSION: Run WindowsShell.Tests.ps1 and the supported shell build using pinned own-worktree dependencies -> pass; 42 executable source suites, including 303 App tests.

These are post-hoc sensitivity controls, not a claim of test-first development. The coordinator independently reviewed the final changes and reran the 303-test app/accessibility suite.

Limitations

Live validation failed at foreground acquisition before UIA root access. No live proof is claimed for UIA SetFocus/reentrant-event completion, F6/Jump activation, rendered focus pixels, sidebar effects, or provider-backed workspace/panel behavior.

The pretranslation tests use an explicit eligibility seam. The hidden-HWND test proves actual Tab accelerator dispatch, not actual header focus delivery.

Deferred live tooling and evidence remain outside this PR. Cross-project worktree-notice aggregation, unsupported summary/board/mailroom panel content, and macOS visual matching remain follow-up work.

Reviewed head: 29ba387.
Commit includes DCO sign-off and Copilot coauthor.