fix(desktop): gate messaging session polling

[izumi0uu]

What does this PR do?

Gates the desktop's broad messaging-session polling so it only runs when there is evidence that messaging needs live updates: the Messaging view is open, the active stored session is a messaging thread, messaging rows are already loaded, or the existing /api/status snapshot reports a configured gateway platform.

This keeps inbound Telegram/WeChat/Discord sessions live for configured messaging users while avoiding the always-on 10s cross-profile session scan for desktop users who are not using messaging.

Related Issue

Fixes #58309

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• Added shouldPollMessagingSessions in apps/desktop/src/app/desktop-controller-utils.ts.
• Used that helper in apps/desktop/src/app/desktop-controller.tsx before arming the 10s messaging-session interval.
• Added focused Vitest coverage for the idle false case and the preserved live-update gates.

How to Test

1. npm --workspace apps/desktop run test:ui -- src/app/desktop-controller-utils.test.ts
2. npm --workspace apps/desktop exec eslint -- src/app/desktop-controller-utils.ts src/app/desktop-controller-utils.test.ts src/app/desktop-controller.tsx
3. git diff --check

Note: npm --workspace apps/desktop run typecheck currently fails before this patch in this lane because workspace dependencies such as @codemirror/*, @xterm/addon-serialize, and fflate are not resolvable.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS (desktop TS/Vitest checks)

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — N/A
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide
• I've updated tool descriptions/schemas if I changed tool behavior — N/A

Screenshots / Logs

Targeted validation:

npm --workspace apps/desktop run test:ui -- src/app/desktop-controller-utils.test.ts
Test Files  1 passed (1)
Tests  9 passed (9)

npm --workspace apps/desktop exec eslint -- src/app/desktop-controller-utils.ts src/app/desktop-controller-utils.test.ts src/app/desktop-controller.tsx
# no output / exit 0