fix: include MCP tools in /v1/tools endpoint so they appear in web UI

[mricharz]

Summary

• MCP tools discovered from external servers (configured in [tools.mcp]) were injected into managed agent streaming requests but never listed in the GET /v1/tools API response, making them invisible in the agent creation wizard
• The list_tools() endpoint now calls _get_mcp_tools() to lazily discover and cache MCP tools, appending them with source: "mcp" and category: "mcp"
• Frontend shows MCP tools under a new MCP / External category with proper search, responsive layout, and visual improvements

Changes

Backend (agent_manager_routes.py):

• Add _get_mcp_tools(app_state) — lazy MCP tool discovery with per-process caching on app_state
• Update list_tools() to accept Request, call _get_mcp_tools(), and append results
• Graceful fallback: if MCP discovery fails, built-in tools still returned

Frontend (AgentsPage.tsx, api.ts):

• Add 'MCP / External' category to tool picker with auto-detection via source === 'mcp'
• Add search/filter input with whitespace AND-matching (e.g. "ha get" matches ha_get_state)
• Responsive dialog width (md:max-w-2xl lg:max-w-3xl) and 3-column tool grid on large screens
• Wrap tools section in bordered container for visual separation
• Budget field uses info tooltip instead of hint text (consistent with other fields)
• Extended ToolInfo.source type to include 'mcp'

Tests (test_tools_endpoint.py):

• test_tools_includes_mcp_tools: verifies MCP tools appear in /v1/tools with correct fields
• test_tools_graceful_mcp_failure: verifies built-in tools returned when MCP is unavailable

Test plan

• pytest tests/server/test_tools_endpoint.py -v — all tests pass
• Configure an MCP server in config.toml, verify tools appear at GET /v1/tools with source: "mcp"
• Open agent creation wizard, verify MCP tools shown under "MCP / External" category
• Test search with spaces (e.g. "ha get") matches underscore-separated tool names
• Verify budget/learning fields aligned on wide screens

[robbym-dev]

Hey @mricharz — thanks for this! The MCP tool discovery and frontend integration look solid, and all tests pass.

A couple things before we can merge:

1. Rebase needed — there are merge conflicts in agent_manager_routes.py and AgentsPage.tsx since both files have changed significantly on main.
2. Add logging for MCP failures — the except Exception: pass in _get_mcp_tools() silently swallows errors, which makes it hard to debug misconfigured MCP servers. Could you add a logger.warning(...) there?

Let us know if you need any help with the rebase!