feat(browser): multi-provider cloud browser support + Browser Use integration

Introduce a cloud browser provider abstraction so users can switch
between Local Browser, Browserbase, and Browser Use (or future providers)
via hermes tools / hermes setup.

Cloud browser providers are behind an ABC (tools/browser_providers/base.py)
so adding a new provider is a single-file addition with no changes to
browser_tool.py internals.

Changes:
- tools/browser_providers/ package with ABC, Browserbase extraction,
  and Browser Use provider
- browser_tool.py refactored to use _PROVIDER_REGISTRY + _get_cloud_provider()
  (cached) instead of hardcoded _is_local_mode() / _create_browserbase_session()
- tools_config.py: generic _is_provider_active() / _detect_active_provider_index()
  replace TTS-only logic; Browser Use added as third browser option
- config.py: BROWSER_USE_API_KEY added to OPTIONAL_ENV_VARS + show_config + allowlist
- subprocess pipe hang fix: agent-browser daemon inherits pipe fds,
  communicate() blocks. Replaced with Popen + temp files.

Original PR: #1208
Co-authored-by: ShawnPana <shawnpana@users.noreply.github.com>

tools/browser_providers/__init__.py

@@ -0,0 +1,10 @@
+"""Cloud browser provider abstraction.
+
+Import the ABC so callers can do::
+
+    from tools.browser_providers import CloudBrowserProvider
+"""
+
+from tools.browser_providers.base import CloudBrowserProvider
+
+__all__ = ["CloudBrowserProvider"]