fix: add missing parseAgentFrontmatter import causing black screen

[avrum]

Problem

When navigating between agents in Cooper's UI, the app goes completely black (no crash, just blank screen). The main.log shows hundreds of ReferenceError: parseAgentFrontmatter is not defined errors.

Additionally, clicking MCP servers crashes with TypeError: Cannot read properties of undefined (reading '0') when server.tools is undefined.

Root Cause

Black Screen (Agent Navigation)

parseAgentFrontmatter is used at 5 locations in src/main/main.ts (lines 879, 1577, 1875, 2731, 2842) but was never imported — only getAllAgents was imported from ./agents. There was also a duplicate getAllAgents import.

The bundler (electron-vite/esbuild) renames the agents.ts export to parseAgentFrontmatter$1 in the bundle, but the unimported direct references in main.ts remain as parseAgentFrontmatter (undefined at runtime). This causes a ReferenceError flood every time sessions are resumed or agents are loaded.

Combined with no React ErrorBoundary in the renderer, cascading failures result in a total black screen.

MCP Panel Crash

server.tools[0] is accessed without checking if server.tools is defined. The MCPServerConfigBase type declares tools: string[] but runtime data can have tools: undefined, causing a TypeError when opening the MCP panel.

Changes

1. src/main/main.ts: Added parseAgentFrontmatter to the import from ./agents and removed the duplicate getAllAgents import
2. src/renderer/components/ErrorBoundary.tsx: New ErrorBoundary component to catch uncaught render errors and show a recovery UI instead of a black screen
3. src/renderer/main.tsx: Wrapped the app with ErrorBoundary
4. src/renderer/App.tsx: Added optional chaining for server.tools access at two locations to prevent TypeError when MCP server config has undefined tools

ErrorBoundary Recovery UI

Instead of a black screen, users now see this recovery screen when an uncaught render error occurs:

┌──────────────────────────────────────────────────────────────────┐
│                                                                  │
│                                                                  │
│                     Something went wrong                         │
│                                                                  │
│       An unexpected error occurred. You can try dismissing       │
│                   this or reloading the app.                     │
│                                                                  │
│      ┌──────────────────────────────────────────────────┐        │
│      │ ReferenceError: parseAgentFrontmatter is not     │        │
│      │ defined                                          │        │
│      │   at resumeSession (main/index.js:22290:31)      │        │
│      │   at async startEarlySessionResumption           │        │
│      │   (main/index.js:21684:5)                        │        │
│      └──────────────────────────────────────────────────┘        │
│                                                                  │
│                  [ Dismiss ]    [ Reload ]                        │
│                                                                  │
└──────────────────────────────────────────────────────────────────┘

The component:

• Shows the error message in a scrollable box (max 8rem)
• Dismiss — attempts to recover by clearing the error state
• Reload — reloads the entire app via window.location.reload()
• Logs full error + component stack to console for debugging

Verification

• Build passes ✅
• All 395 unit tests pass ✅
• TypeScript no longer reports TS2304: Cannot find name 'parseAgentFrontmatter' errors
• Bundle now correctly resolves all parseAgentFrontmatter references to the same function
• MCP panel handles servers with undefined tools gracefully ✅