fix(desktop): keep model picker switches session-scoped

[izumi0uu]

What does this PR do?

Fixes the desktop model picker path for live sessions so selecting a model, including a MoA preset, stays session-scoped instead of falling through to the global config.yaml persist path.

The desktop hook was already sending session_id to config.set, but the gateway decides global persistence from the parsed model flags. Without --session, resolve_persist_behavior(False, False) can still persist the switch globally when model.persist_switch_by_default is enabled. This PR appends --session for active desktop sessions and adds coverage for both normal provider selections and MoA presets.

This intentionally does not change Telegram sticky-session migration or MoA fallback behavior; it closes the desktop-to-global bleed entry point described in the issue.

Related Issue

Fixes #59480

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✅ Tests (adding or improving test coverage)

Changes Made

• apps/desktop/src/app/session/hooks/use-model-controls.ts
  • Append --session when the desktop picker applies a model switch to an active session.
• apps/desktop/src/app/session/hooks/use-model-controls.test.tsx
  • Assert active-session provider switches include --session.
  • Add a MoA preset regression test proving BeastMode --provider moa --session is sent.
• apps/desktop/src/app/shell/model-menu-panel.tsx
  • Update the MoA preset comment to reflect the live-session scoped path.
• apps/desktop/src/app/shell/model-menu-panel.test.tsx
  • Clarify the existing MoA picker routing assertion.

How to Test

1. cd apps/desktop && npm run test:ui -- src/app/session/hooks/use-model-controls.test.tsx src/app/shell/model-menu-panel.test.tsx
2. cd apps/desktop && npm run typecheck
3. git diff --check

Additional source-level probe used during development:

BeastMode --provider moa
  parsed= BeastMode moa global= False session= False
  persist_global= True
BeastMode --provider moa --session
  parsed= BeastMode moa global= False session= True
  persist_global= False

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
• I've tested on my platform: macOS Darwin 24.6.0 arm64

Documentation & Housekeeping

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

[linfeng961]

Thanks for the PR

[teknium1]

Merged via PR #62694. Your Desktop and MoA commit was cherry-picked onto current main with authorship preserved, then widened to every TUI picker path. Thank you for the focused fix.