feat: unify web tool config under WebToolsConfig + add web tool toggle controls

- Rename WebSearchConfig references to the new WebToolsConfig root struct that wraps both search config and global proxy settings
- Add 'enable' flag to WebToolsConfig to allow fully disabling all web-related tools (WebSearch, WebFetch) at runtime
- Update AgentLoop and SubagentManager to receive the full web config object instead of separate web_search_config/web_proxy parameters
- Update CLI command initialization to pass the consolidated web config struct instead of split fields
- Change default web search provider from brave to duckduckgo for better out-of-the-box usability (no API key required)

nanobot/cli/commands.py

@@ -541,8 +541,7 @@ def gateway(
         model=config.agents.defaults.model,
         max_iterations=config.agents.defaults.max_tool_iterations,
         context_window_tokens=config.agents.defaults.context_window_tokens,
-        web_search_config=config.tools.web.search,
-        web_proxy=config.tools.web.proxy or None,
+        web_config=config.tools.web,
         exec_config=config.tools.exec,
         cron_service=cron,
         restrict_to_workspace=config.tools.restrict_to_workspace,
@@ -747,8 +746,7 @@ def agent(
         model=config.agents.defaults.model,
         max_iterations=config.agents.defaults.max_tool_iterations,
         context_window_tokens=config.agents.defaults.context_window_tokens,
-        web_search_config=config.tools.web.search,
-        web_proxy=config.tools.web.proxy or None,
+        web_config=config.tools.web,
         exec_config=config.tools.exec,
         cron_service=cron,
         restrict_to_workspace=config.tools.restrict_to_workspace,