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/adapters/http.md

@@ -0,0 +1,53 @@
+---
+title: HTTP Adapter
+summary: HTTP webhook adapter
+---
+
+# HTTP Adapter
+
+The `http` adapter sends a webhook request to an external agent service. The agent runs externally and Paperclip just triggers it.
+
+## When to Use
+
+- Agent runs as an external service (cloud function, dedicated server)
+- Fire-and-forget invocation model
+- Integration with third-party agent platforms
+
+## When Not to Use
+
+- If the agent runs locally on the same machine (use `process`, `claude_local`, or `codex_local`)
+- If you need stdout capture and real-time run viewing
+
+## Configuration
+
+| Field | Type | Required | Description |
+|-------|------|----------|-------------|
+| `url` | string | Yes | Webhook URL to POST to |
+| `headers` | object | No | Additional HTTP headers |
+| `timeoutSec` | number | No | Request timeout |
+
+## How It Works
+
+1. Paperclip sends a POST request to the configured URL
+2. The request body includes the execution context (agent ID, task info, wake reason)
+3. The external agent processes the request and calls back to the Paperclip API
+4. Response from the webhook is captured as the run result
+
+## Request Body
+
+The webhook receives a JSON payload with:
+
+```json
+{
+  "runId": "...",
+  "agentId": "...",
+  "companyId": "...",
+  "context": {
+    "taskId": "...",
+    "wakeReason": "...",
+    "commentId": "..."
+  }
+}
+```
+
+The external agent uses `PAPERCLIP_API_URL` and an API key to call back to Paperclip.