Create Omni/Agents/Web.hs - main agents web surface

Create Omni/Agents/Web.hs — the main agents web surface. This is the WAI app that handles /agents/* routes.

Routes

• GET /agents → Dashboard (active agents, recent agents, stats)
• GET /agents/:id → Agent detail page
• GET /agents/new → Spawn form
• POST /agents/spawn → Spawn agent (calls Agentd daemon API)
• POST /agents/:id/send → Send message (calls daemon API)
• POST /agents/:id/stop → Stop agent (calls daemon API)
• GET /agents/:id/events → HTMX partial for live event polling
• GET /agents/:id/diff → Show git diff for agent's worktree
• GET /agents/:id/files → File browser for worktree
• Subnav: "interactive" (active, default), "pipeline" (links to existing pipeline page)

Architecture

• WAI app similar to Omni/Pipeline/Web.hs
• Calls Agentd daemon HTTP API (localhost:8400) for agent management
• Reads event logs from daemon's log directory for display
• Uses Omni.Web.Style.sharedShellWithSubnav for layout
• Uses htmx for live updates and form submissions

Design

• Use the shared Omni.Web.Style design system (ef-dream theme)
• Dashboard: stats bar (running, idle, completed, total cost), then list of agents
• Agent cards show: run ID, status badge, prompt preview, cost, elapsed time
• Full-width, information-dense, mobile-friendly (like pipeline page)

Dependencies

• Omni.Web.Style for shell/nav/CSS
• http-conduit or http-client to call daemon API
• aeson for JSON parsing
• lucid for HTML
• wai for request handling