Raise desktop test coverage to 80%

[VincentShipsIt]

Goal

Raise the desktop app test coverage target from the current 65% gate to 80% across lines, statements, functions, and branches.

Current baseline

Latest desktop coverage after the coverage push:

• Lines: 74.32%
• Statements: 72.00%
• Functions: 71.43%
• Branches: 65.89%

Repo aggregate with the new 65% threshold passes:

• Lines: 78.55%
• Statements: 76.16%
• Functions: 75.51%
• Branches: 66.83%

Suggested focus areas

• Desktop main entry/orchestration: apps/desktop/src/main/index.ts, apps/desktop/src/main/ipc.ts
• Large IPC handlers: register-github-handlers.ts, register-pipeline-handlers.ts, register-project-handlers.ts
• Remaining renderer gaps: IssuesPanel, ProjectSidebar, ProjectSettingsModal, TerminalTranscript, create-automation-modal

Acceptance criteria

• Desktop coverage reaches at least 80% for lines, statements, functions, and branches.
• The repo coverage threshold can be raised from 65% to 80% without failing node scripts/coverage-summary.mjs.
• New tests cover behavior and edge cases, not implementation details.

Priority: P3.