feat(desktop): sync terminal chrome with the app theme

[RaspberryLee]

Summary

Align the integrated terminal chrome with the desktop application theme.

This removes the decorative macOS traffic-light dots from the terminal toolbar, replaces text-heavy actions with accessible icon controls, and keeps xterm colors synchronized with the active light or dark application theme. The terminal process and PTY behavior are unchanged.

Feature Quality Contract

• Changed surface: desktop UI
• Tests added or updated:
  • desktop/src/pages/TerminalSettings.test.tsx
  • cd desktop && bun run test -- --run src/pages/TerminalSettings.test.tsx — 18 passed, 0 failed
• Coverage evidence:
  • bun run check:impact selected check:desktop and check:coverage.
  • Standalone production build passed: cd desktop && bun run build.
  • Full check:desktop lint passed, then the suite reported 2,092 passed, 364 failed, 2 skipped. Failures are dominated by the current Node 26 environment exposing localStorage as unavailable, Windows symlink EPERM, and existing Mermaid/test timeouts.
  • Local coverage report: artifacts/coverage/2026-07-23T08-59-37-631Z/coverage-report.md; desktop instrumentation failed in the same environment, so changed-line coverage was unavailable locally.
• E2E / live-model evidence:
  • Live model: not run (untrusted fork / no provider)
  • Visual desktop smoke was not recorded in the isolated PR worktree.
• Known risk / rollback:
  • Visual behavior changes are limited to terminal chrome and xterm theme synchronization. Reverting this commit restores the previous toolbar and colors.

Verification

• I ran the relevant local checks, or explained why they did not fully pass.
• I added or updated same-area tests for every production behavior change.
• I ran the checks selected by bun run check:impact; environmental blockers are documented above.
• Changed-line coverage could not be produced because desktop coverage instrumentation failed in the local Node 26 environment.
• I summarized the relevant suite and report results.
• Focused deterministic UI tests and the production build passed; live-model testing does not apply.

Risk

• This PR does not touch CLI core paths.
• Production code changes include matching tests.
• Coverage baseline/threshold files are unchanged.
• Quarantine policy is unchanged.
• Provider/runtime code is unchanged.

[github-actions]

PR quality triage

Changed areas: area:desktop

CLI core policy: No CLI-core policy block detected.

Missing-test policy: No missing-test policy block detected.

Coverage baseline policy: No coverage-baseline policy block detected.

CLI core files:

• none

Coverage policy files:

• none

Required check plan:

• See PR Quality / scope-plan; it is the single source of truth for selected jobs.

Test coverage signals:

• No obvious missing-test signal from changed paths.

Risk notes:

• No special risk notes from changed paths.

Hard merge gates come from the deterministic GitHub Actions contract lanes above.