fix(web-ui): support font size shortcuts and disable printing

[kev1n77]

Summary

• Support Ctrl +/- on Windows/Linux and Command +/- on macOS to adjust UI font size.
• Accept the unshifted = key and numeric keypad add/subtract keys.
• Disable Ctrl/Command+P printing.
• Keep the font settings controls and preview synchronized with shortcut changes.

Type and Areas

Type: Bug fix / UI/UX

Areas: Web UI, shared desktop frontend

Motivation / Impact

Users can adjust typography with familiar keyboard shortcuts, including while an input or editor is focused. Each press changes the base font size by 1px within the existing 12–20px range and saves it through the existing font preference service.

Print shortcuts no longer open the browser print dialog.

Verification

• pnpm --dir src/web-ui run test:run src/app/browserShortcutPolicy.test.ts src/infrastructure/font-preference/core/FontPreferenceService.test.ts src/infrastructure/font-preference/components/FontPreferencePanel.test.tsx
  • Passed: 3 files, 46 tests covering platform modifiers, key variants, event interception, IME exclusions, size limits, persistence calls, repeated adjustments, and settings synchronization.
• pnpm run check:web
  • Passed, with existing Appearance contract warnings in unrelated files.
• git diff --check
  • Passed.

Reviewer Notes

Reuses the existing font preference schema and typography tokens; no migration or new host API is required.

Platform keyboard behavior was covered by automated DOM tests. Native Windows/macOS clients and remote workspace, remote control, Peer Device Mode, and Detached Dispatch scenarios were not manually exercised.

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. No copy or locale changes are required.