browser: replace browser-use agent with native browser

Introduce the new built-in Browser plugin for Agent Zero, replacing the legacy
browser-use-based browser agent with a direct Playwright-powered browser tool,
live WebUI viewer, browser session controls, status APIs, configuration, and
extension-management support.

Add browser-specific modal behavior so the browser can run as a floating,
resizable, no-backdrop window, including modal focus, toggle, and idempotent
open helpers for richer WebUI surfaces.

Remove the old `_browser_agent` core plugin and the `browser-use` dependency,
then clean up stale browser-model wiring and references across agent code,
model configuration docs, setup guides, troubleshooting docs, skills, and
Agent Zero knowledge.

Update regression and WebUI extension-surface coverage for the new browser
architecture and modal behavior.

The legacy browser-use implementation has been extracted from core so it can
continue separately as a community plugin published through the A0 Plugin Index for any user or professional that were relying on it for workflow.

plugins/_browser/api/status.py

@@ -0,0 +1,32 @@
+from helpers.api import ApiHandler, Request
+from plugins._browser.helpers.config import build_browser_launch_config, get_browser_config
+from plugins._browser.helpers.playwright import get_playwright_binary, get_playwright_cache_dir
+from plugins._browser.helpers.runtime import known_context_ids
+
+
+class Status(ApiHandler):
+    async def process(self, input: dict, request: Request) -> dict:
+        browser_config = get_browser_config()
+        launch_config = build_browser_launch_config(browser_config)
+        runtime_binary = get_playwright_binary(
+            full_browser=launch_config["requires_full_browser"]
+        )
+        shell_binary = get_playwright_binary(full_browser=False)
+        chromium_binary = get_playwright_binary(full_browser=True)
+        return {
+            "plugin": "_browser",
+            "playwright": {
+                "cache_dir": get_playwright_cache_dir(),
+                "binary_found": bool(runtime_binary),
+                "binary_path": str(runtime_binary) if runtime_binary else "",
+                "headless_shell_binary_path": str(shell_binary) if shell_binary else "",
+                "chromium_binary_path": str(chromium_binary) if chromium_binary else "",
+                "launch_mode": launch_config["browser_mode"],
+            },
+            "extensions": {
+                **launch_config["extensions"],
+                "launch_mode": launch_config["browser_mode"],
+                "requires_full_browser": launch_config["requires_full_browser"],
+            },
+            "contexts": known_context_ids(),
+        }