Add runtime stream enable/disable/status commands (#951)

* Add runtime stream management commands

* Run rustfmt and satisfy clippy

* Fix stream disable cleanup semantics

* Format stream disable regression tests

docs/src/app/commands/page.mdx

@@ -30,6 +30,9 @@ agent-browser pdf <path>              # Save page as PDF
 agent-browser snapshot                # Accessibility tree with refs
 agent-browser eval <js>               # Run JavaScript
 agent-browser connect <port|url>      # Connect to browser via CDP
+agent-browser stream enable [--port <port>]  # Start runtime WebSocket streaming
+agent-browser stream status           # Show runtime streaming state and bound port
+agent-browser stream disable          # Stop runtime WebSocket streaming
 agent-browser close                   # Close browser (aliases: quit, exit)
 ```
 
@@ -228,6 +231,17 @@ agent-browser dialog status           # Check if a dialog is currently open
 
 When a JavaScript dialog (`alert`, `confirm`, `prompt`) is pending, all command responses include a `warning` field with the dialog type and message.
 
+## Streaming
+
+```bash
+agent-browser stream enable           # Start runtime WebSocket streaming on an auto-selected port
+agent-browser stream enable --port 9223  # Bind a specific localhost port
+agent-browser stream status           # Show enabled state, port, browser connection, screencasting
+agent-browser stream disable          # Stop runtime streaming and remove the .stream metadata file
+```
+
+Use `stream enable` for sessions that are already running. If you need streaming from daemon startup, set `AGENT_BROWSER_STREAM_PORT` before the first command in that session.
+
 ## Debug
 
 ```bash

docs/src/app/configuration/page.mdx

@@ -173,7 +173,7 @@ These environment variables configure additional daemon and runtime behavior:
     <tr><td><code>AGENT_BROWSER_ENCRYPTION_KEY</code></td><td>64-char hex key for AES-256-GCM session encryption.</td><td>(none)</td></tr>
     <tr><td><code>AGENT_BROWSER_EXTENSIONS</code></td><td>Comma-separated browser extension paths. Extensions work in both headed and headless mode.</td><td>(none)</td></tr>
     <tr><td><code>AGENT_BROWSER_HEADED</code></td><td>Show browser window instead of running headless (<code>1</code> to enable).</td><td>(disabled)</td></tr>
-    <tr><td><code>AGENT_BROWSER_STREAM_PORT</code></td><td>Enable WebSocket streaming on the specified port (e.g., <code>9223</code>).</td><td>(disabled)</td></tr>
+    <tr><td><code>AGENT_BROWSER_STREAM_PORT</code></td><td>Enable WebSocket streaming at daemon startup on the specified port (e.g., <code>9223</code>). For an already-running session, use <code>agent-browser stream enable</code>.</td><td>(disabled)</td></tr>
     <tr><td><code>AGENT_BROWSER_IDLE_TIMEOUT_MS</code></td><td>Auto-shutdown the daemon after N ms of inactivity (no commands received). Useful for ephemeral environments.</td><td>(disabled)</td></tr>
     <tr><td><code>AGENT_BROWSER_IOS_DEVICE</code></td><td>Default iOS device name for the <code>ios</code> provider.</td><td>(none)</td></tr>
     <tr><td><code>AGENT_BROWSER_IOS_UDID</code></td><td>Default iOS device UDID for the <code>ios</code> provider.</td><td>(none)</td></tr>

docs/src/app/streaming/page.mdx

@@ -5,14 +5,46 @@ where a human can watch and interact alongside an AI agent.
 
 ## Enable streaming
 
-Set the `AGENT_BROWSER_STREAM_PORT` environment variable to start
-a WebSocket server:
+For an already-running session, enable streaming at runtime:
+
+```bash
+agent-browser stream enable
+agent-browser stream status
+agent-browser stream disable
+```
+
+`stream enable` binds an available localhost port automatically unless you pass `--port <port>`. `stream status` returns the enabled state, active port, browser connection state, and whether screencasting is active. `stream disable` tears the server down and removes the session's `.stream` metadata file.
+
+If you want the WebSocket server to exist from daemon startup, set `AGENT_BROWSER_STREAM_PORT` before the first command in that session:
 
 ```bash
 AGENT_BROWSER_STREAM_PORT=9223 agent-browser open example.com
 ```
 
-The server streams viewport frames and accepts input events (mouse, keyboard, touch).
+The environment variable only affects daemon startup. For sessions that are already running, use `agent-browser stream enable` instead.
+
+Once enabled, the server streams viewport frames and accepts input events (mouse, keyboard, touch).
+
+## Runtime status response
+
+`agent-browser stream status --json` returns data like:
+
+```json
+{
+  "enabled": true,
+  "port": 9223,
+  "connected": true,
+  "screencasting": true
+}
+```
+
+`connected` reports whether the daemon currently has a browser attached. `screencasting` reports whether frames are actively being produced for the stream server.
+
+## Relationship to screencast commands
+
+`stream enable` creates the WebSocket server and keeps it available for the session. WebSocket clients then trigger live frame delivery automatically.
+
+The lower-level `screencast_start` and `screencast_stop` commands still control explicit CDP screencasts directly. Use them when you want a screencast without the WebSocket runtime server.
 
 ## WebSocket protocol