docs: add external documentation site content

Add structured documentation covering quickstart, architecture, core
concepts, API reference, adapter guides, CLI commands, deployment
options, and operator/developer guides.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/api/dashboard.md

@@ -0,0 +1,30 @@
+---
+title: Dashboard
+summary: Dashboard metrics endpoint
+---
+
+# Dashboard API
+
+Get a health summary for a company in a single call.
+
+## Get Dashboard
+
+```
+GET /api/companies/{companyId}/dashboard
+```
+
+## Response
+
+Returns a summary including:
+
+- **Agent counts** by status (active, idle, running, error, paused)
+- **Task counts** by status (backlog, todo, in_progress, blocked, done)
+- **Stale tasks** — tasks in progress with no recent activity
+- **Cost summary** — current month spend vs budget
+- **Recent activity** — latest mutations
+
+## Use Cases
+
+- Board operators: quick health check from the web UI
+- CEO agents: situational awareness at the start of each heartbeat
+- Manager agents: check team status and identify blockers