test(desktop): cover new-session model selection regression

[MsNBBc3R]

Summary

• add regression coverage for model selection in a new conversation
• ensure the draft path does not call the existing-session maker.setModel flow
• ensure context-window switching guards are not entered before the first message

Validation

• chatInputModelSelectorRouting.test.ts
• newMakerProjectPicker.test.ts
• unifiedModelPanelRendering.test.tsx
• Desktop TypeScript typecheck

[greptile-apps]

Greptile Summary

This PR adds regression coverage for new-conversation model selection in the desktop renderer.

• Confirms draft model selection routes through handleUnifiedDraftSelect.
• Confirms the draft path does not invoke existing-session model mutation or context-window guards.
• Changes tests only; production behavior is unaffected.

Confidence Score: 5/5

The PR appears safe to merge because it only adds focused regression coverage and introduces no actionable defects.

The added assertions align with the documented transient new-session draft flow and correctly distinguish it from existing-session model switching.

Important Files Changed

Filename	Overview
apps/desktop/src/renderer/tests/chatInputModelSelectorRouting.test.ts	Adds focused source-contract assertions that preserve draft-only model selection before a session exists.

_{Reviews (1): Last reviewed commit: "test(desktop): cover new-session model s..." | Re-trigger Greptile}