feat(mcp): add browser OAuth for remote servers (#5316)

docs/guides/configure-mcp-tools.md

@@ -30,10 +30,15 @@ remote HTTP endpoint.
 For local interactive setup:
 
 1. Run `nanobot webui` and open **Apps**.
-2. Choose a known integration preset, or add a custom stdio, HTTP, or SSE server.
+2. Choose a known MCP server preset, or add a custom stdio, HTTP, or SSE server.
+   For a custom OAuth server, choose **OAuth** under **Authentication**, save it,
+   and click **Connect**. Presets such as Xmind, Notion, and Linear go straight to
+   **Connect**. Approve access in the browser window. HTTPS and localhost WebUIs
+   return automatically. From a remote plain-HTTP WebUI, copy the complete
+   localhost callback URL from the browser address bar and paste it into nanobot.
 3. Limit the enabled tools when the server exposes more than the task needs.
 4. Save and restart when prompted.
-5. Mention the integration with `@` in the next message and ask for a small test action.
+5. Mention the connected MCP server with `@` in the next message and ask for a small test action.
 
 For manual or deployment-managed config, add this to `~/.nanobot/config.json`:
 
@@ -58,12 +63,16 @@ Restart nanobot and ask a question that requires the MCP tool.
 - Prefer `enabledTools` over exposing every tool by default.
 - Use `toolTimeout` for slow MCP operations.
 - Use HTTP MCP only for endpoints you trust.
+- For deployment-managed OAuth servers, set `auth` to `oauth` and complete the
+  browser connection from **Apps → MCP**.
 - Keep MCP server commands stable and versioned in deployment docs or scripts.
 
 ## Security notes
 
 - Stdio MCP starts a local process; review the command before enabling it.
-- HTTP/SSE MCP uses nanobot's SSRF guard.
+- HTTP/SSE MCP uses nanobot's SSRF guard, including OAuth discovery, registration,
+  token exchange, and redirects.
+- OAuth credentials live in the nanobot data directory, not in `config.json`.
 - Allow private HTTP MCP hosts only with narrow `tools.ssrfWhitelist` CIDRs.
 - Do not place secrets in command arguments when environment variables or
   headers can be used.