[Feature]: Option to disable Chrome tab group creation ("OpenCLI Browser" orange group)

## Feature Request

### Problem

Every time OpenCLI opens a browser tab via `opencli browser open ...`, the Chrome extension creates (or reuses) a **tab group** named **"OpenCLI Browser"** with orange color. Over time, empty/abandoned groups accumulate in Chrome, cluttering the tab bar:

- Restarting Chrome → old window gone, new window + new group created next time
- Using different session names → potentially multiple groups
- No way to prevent this behavior

This is especially disruptive for users who already have structured tab management (e.g., custom manual groups, Tab Groups for projects) — the auto-created "OpenCLI Browser" group feels invasive.

### Root Cause

In the Chrome extension's `background.js`:

```
const CONTAINER_TAB_GROUP_TITLE = {
interactive: "OpenCLI Browser",
automation: "OpenCLI Adapter",
};
const OWNED_TAB_GROUP_COLOR = "orange";
```

The `ensureOwnedContainerGroup()` → `createOwnedGroup()` path always creates/ensures a tab group. There is no configuration to opt out.

### Requested Solution

Add a **configuration option** to disable automatic tab group creation, ideally in one of these forms:

1. **Environment variable** — e.g. `OPENCLI_NO_TAB_GROUP=1` (simplest, easy to set in .zshrc)
2. **CLI flag** — e.g. `opencli --no-group browser open ...` or through the `--profile` mechanism
3. **Extension preference** — a toggle stored via chrome.storage.local that the CLI can set once

### Behavior When Disabled

When the option is active:
- The extension still manages its own owned Chrome window
- Tabs are opened in that window normally, but **not grouped** into a named/colored tab group
- All other functionality (session management, tab lease, idle timeout) remains unchanged

### Workaround

Users can currently use `opencli browser bind` to bind to an existing tab (avoids creating new windows/groups), but this is not suitable for all workflows (e.g. automation, multi-session browsing).

### Environment

- OpenCLI: (check with `opencli --version`)
- Extension: 1.0.21
- Chrome: latest

Start in the Chrome extension's background.js and trace ensureOwnedContainerGroup() through createOwnedGroup(), then inspect the opencli browser open flow and its configuration entry points. Done means an explicit opt-out prevents named or colored group creation while preserving the owned window, tabs, session management, tab lease, and idle timeout behavior.

Written by the indexing model from the issue text.