fix(web-ui): add branch picker refresh and preserve selected styling

[bobleer]

Summary

The composer branch picker has no refresh action, and hovering or using keyboard navigation overrides the current branch's selected background. Add a refresh button beside search and preserve the selected background across hover, press, and virtual keyboard focus.

Type and Areas

Type: bug fix / UI/UX

Areas: Web UI, shared design system

Motivation / Impact

• Refresh branches without closing the picker or clearing the search. Display loading state and prevent duplicate clicks.
• Keep the last successful list on refresh failure, show an actionable error, and allow retry. Initial failures no longer appear as an empty repository.
• Ignore responses from a previous workspace or a closed picker.
• Keep search and refresh keyboard-accessible; Enter on refresh cannot also switch the highlighted branch.
• Use the existing workspace-aware Git service and retain its legacy error fallback for other callers. Refresh rereads repository refs; it does not fetch from remotes.

Verification

• pnpm --dir src/web-ui run test:run src/tools/git/components/BranchQuickSwitch.test.tsx src/tools/git/services/GitService.test.ts src/shared/ui/MenuComposition.contract.test.ts — 28 tests passed.
• node --test design-system/packages/ui/tests/listbox.test.mjs — 4 tests passed.
• pnpm --dir src/web-ui run icons:check — passed.
• pnpm --dir src/web-ui exec vitest run src/infrastructure/design-system/IconUsageIntegration.test.tsx src/app/startup/startupPreload.test.ts — 21 tests passed.
• pnpm run check:web — passed, including TypeScript, Appearance contracts, theme colors, and visual governance.
• pnpm run i18n:audit — passed with no warnings.
• pnpm run motion:audit — inventory reviewed; no new animation was introduced.
• git diff --check — passed.

Reviewer Notes

AI-assisted implementation, tested with focused unit/DOM tests and repository checks. No live GUI before/after capture was performed, so screenshots are unavailable. Tests exercise workspace scope forwarding and stale response handling with mocks; remote workspace, remote control, Peer Device Mode, and Detached Dispatch were not exercised end to end.

The Listbox fix lowers transient interaction selector specificity while keeping forced-colors overrides intact. English, Simplified Chinese, and Traditional Chinese copy is updated. No persisted or wire-format changes are required.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.