Worktree diff view and file browser

Show the git diff and a file browser for an agent's worktree.

Diff View (GET /agents/:id/diff)

• Run git diff HEAD in the agent's worktree path (from AgentInfo.workspace)
• Also run git diff --stat HEAD for a summary
• Render as:

1. Stat summary at top (files changed, insertions, deletions) 2. Full unified diff with syntax-highlighted hunks 3. Each file in its own collapsible section

• Use <pre> with diff coloring: green for additions, red for deletions, muted for context
• Link to file browser for each changed file

File Browser (GET /agents/:id/files and GET /agents/:id/files/*path)

• List directory contents of the worktree
• Click into subdirectories
• Click files to view contents (syntax highlighted if possible, or just <pre>)
• Show file size, modification time
• Breadcrumb navigation

Security

• Only allow browsing within the worktree path (no path traversal)
• Resolve symlinks and check they stay within worktree

Data Source

• Get workspace path from daemon: GET http://localhost:8400/agents/:id → workspace field
• Shell out to git diff in that workspace
• Use System.Directory for file listing

Integration

• These are tabs/links on the agent detail page
• Can also be htmx partials loaded into the detail page