feat: add performance controls for large browser ops

- Add throttled large-operation handling for tab, group, and session commands.
- Introduce performance profiles, audible-tab aware gentle mode, and job progress tracking.
- Support background session restores with status/cancel commands and lazy placeholders.
- Expose new perf and extension CLI groups plus matching Python SDK methods.
- Preserve pinned tabs during session snapshots and debounce auto-save updates.
- Bump browser-cli and extension versions to 0.10.0 and add pytest-cov to dev deps.
- Add coverage for performance controls, background jobs, lazy restores, and tab metadata.

browser_cli/commands/extension.py

@@ -0,0 +1,21 @@
+import time
+import click
+from rich.console import Console
+from browser_cli.commands import _handle
+
+console = Console()
+
+@click.group("extension")
+def extension_group():
+    """Manage the browser-cli browser extension."""
+
+@extension_group.command("reload")
+def extension_reload():
+    """Reload the browser-cli extension service worker.
+
+    Useful after updating background.js without restarting the browser.
+    The command returns immediately; the extension restarts ~200 ms later.
+    Re-connects automatically via the keepalive alarm within ~25 seconds.
+    """
+    _handle("extension.reload")
+    console.print("[green]Extension reloading…[/green] reconnects automatically")