feat: group multi-browser output by source

- Add browser source grouping metadata to SDK-created tabs, groups,
  list results, and aggregate count results.
- Render grouped local/remote browser tables consistently for clients,
  tabs, groups, windows, sessions, and remote status output.
- Document remote control, auth, HTTP gateway usage, and the refreshed
  project structure in the README.
- Add coverage for grouped output and BrowserCounts browser_groups.
- Bump the Python package, extension manifest, and lockfile to 0.15.6.
- Add a just publish helper for building and publishing release artifacts.

browser_cli/commands/session.py

@@ -105,24 +105,20 @@ def session_diff(name_a, name_b):
 def session_list():
     """List all saved sessions."""
     from datetime import datetime
-    from rich.table import Table
+    from browser_cli.commands.rendering import print_browser_grouped_table_rows
     sessions = client_from_ctx().session.list()
     if not sessions:
         console.print("[yellow]No saved sessions[/yellow]")
         return
-    show_browser = any("browser" in s for s in sessions)
-    table = Table(show_header=True, header_style="bold cyan")
-    if show_browser:
-        table.add_column("Browser")
-    table.add_column("Name")
-    table.add_column("Tabs", width=6)
-    table.add_column("Saved at")
-    for s in sessions:
-        saved = datetime.fromtimestamp(s["savedAt"] / 1000).strftime("%Y-%m-%d %H:%M") if s.get("savedAt") else ""
-        row = [s.get("browser", "")] if show_browser else []
-        row.extend([s["name"], str(s["tabs"]), saved])
-        table.add_row(*row)
-    console.print(table)
+    def saved_at(session):
+        return datetime.fromtimestamp(session["savedAt"] / 1000).strftime("%Y-%m-%d %H:%M") if session.get("savedAt") else ""
+
+    columns = [
+        ("Name", lambda session: session["name"]),
+        ("Tabs", lambda session: session["tabs"]),
+        ("Saved at", saved_at),
+    ]
+    print_browser_grouped_table_rows(sessions, columns, console=console, empty_message="[yellow]No saved sessions[/yellow]")
 
 @session_group.command("remove")
 @click.argument("name")