feat: add CDP tab-group plugin handshake with silent fallback

docs/src/app/commands/page.mdx

@@ -116,7 +116,7 @@ agent-browser wait --download [path]  # Wait for download
 Control how `open`/`navigate` handles verification or captcha interstitials:
 
 ```bash
-agent-browser --risk-mode warn open https://example.com   # default: retry and warn with riskSignals
+agent-browser --risk-mode warn open https://example.com   # default: wait for auto-clear, then retry/warn with riskSignals
 agent-browser --risk-mode block open https://example.com  # fail fast on detection
 agent-browser --risk-mode off open https://example.com    # disable detection/retry
 ```
@@ -134,17 +134,21 @@ Use `--download-path <dir>` (or `AGENT_BROWSER_DOWNLOAD_PATH` env) to set a defa
 
 ```bash
 agent-browser open https://example.com
-# Local Chromium launch auto-groups tabs under "Agent Browser Stealth"
+# CDP mode groups tabs when tab-group plugin is installed
 
 # Override the default group title
 agent-browser --tab-group "My Agent Group" open https://example.com
 ```
 
-Local Chromium launches auto-create/reuse the `Agent Browser Stealth` tab group and move newly opened agent tabs into that group.
+CDP mode uses a browser extension handshake to group tabs.
 
-- Supported only for local Chromium launches.
-- In CDP (`--cdp` / `--auto-connect`) and cloud provider modes, the flag is ignored with a warning.
-- Use `--tab-group` or `AGENT_BROWSER_TAB_GROUP` to override the default group title.
+- Extension available: tabs are grouped by `session`.
+- Extension missing/unavailable: silent no-op (commands still succeed).
+- Default titles:
+  - `default` session: `Agent Browser Stealth`
+  - non-default: `Agent Browser Stealth • <session>`
+- Use `--tab-group` / `AGENT_BROWSER_TAB_GROUP` for base title.
+- Use `AGENT_BROWSER_TAB_GROUP_PLUGIN_ID` (or `--tab-group-plugin-id`) to override expected extension ID.
 
 ## Mouse
 
@@ -276,7 +280,7 @@ agent-browser reload                  # Reload page
 
 ```bash
 --session <name>         # Isolated browser session
---session-name <name>    # Auto-save/restore session state (cookies, localStorage)
+--session-name <name>    # Auto-save/restore session state (defaults to --session when omitted)
 --state <path>           # Load storage state from JSON file
 --headers <json>         # HTTP headers scoped to URL's origin
 --executable-path <path> # Custom browser executable
@@ -296,7 +300,8 @@ agent-browser reload                  # Reload page
 --headed                 # Show browser window (not headless)
 --cdp <port|url>         # Connect via Chrome DevTools Protocol (port or WebSocket URL)
 --auto-connect           # Auto-discover and connect to running Chrome
---tab-group <name>       # Override default agent tab group title (Chromium local launch only)
+--tab-group <name>       # Base title for agent tab groups (CDP plugin mode)
+--tab-group-plugin-id <id> # Expected extension ID for tab-group handshake
 --debug                  # Debug output (includes stealth connection type + capabilities)
 ```