ci: Add MCP server tests workflow (#1506)

* ci: Add MCP server tests workflow

Add dedicated CI workflow for testing the MCP (Model Context Protocol)
server implementation. This workflow:

- Runs on changes to MCP-related files
- Verifies MCP module loads correctly
- Tests discovery tools (list_strategies, list_search_engines, get_configuration)
- Runs full MCP unit test suite with mocks
- Tests MCP strategy (ReAct pattern) implementation
- Verifies server startup behavior

The tests use mocks to avoid requiring an LLM backend, making them
fast and reliable in CI environments.

Prepares CI infrastructure for PR #1366 (MCP server feature).

* refactor: Move MCP smoke tests to external script

Address review feedback from djpetti:
- Extract MCP module loading test to scripts/mcp_smoke_test.sh
- Extract MCP server startup test to the same script
- Update workflow to call the external script
- Add script path to workflow triggers

* ci: skip MCP tests when server module not implemented

The MCP server module (src/local_deep_research/mcp/server.py) is in a
separate feature branch. This change makes the MCP test workflow skip
gracefully when the module doesn't exist, with a clear notice.

Tests will automatically run once the MCP feature branch is merged.

scripts/mcp_smoke_test.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+# MCP Server Smoke Test
+# Verifies that the MCP server module loads correctly and basic tools work
+
+set -e
+
+echo "=== MCP Server Smoke Test ==="
+echo ""
+
+# Test 1: Verify MCP module loads
+echo "1. Testing MCP module loading..."
+python -c "
+from local_deep_research.mcp.server import mcp, list_strategies, get_configuration
+print('   MCP server module loaded successfully')
+print(f'   Server name: {mcp.name}')
+
+# Test discovery tools
+result = list_strategies()
+assert result['status'] == 'success', f'list_strategies failed: {result}'
+print(f'   list_strategies: {len(result[\"strategies\"])} strategies available')
+
+config = get_configuration()
+assert config['status'] == 'success', f'get_configuration failed: {config}'
+print('   get_configuration: works correctly')
+"
+echo "   PASSED"
+echo ""
+
+# Test 2: Verify MCP server startup
+echo "2. Testing MCP server startup..."
+timeout 5 python -m local_deep_research.mcp 2>&1 || {
+    exit_code=$?
+    if [ $exit_code -eq 124 ]; then
+        echo "   Server started correctly (timed out waiting for STDIO input as expected)"
+        echo "   PASSED"
+    else
+        echo "   FAILED: MCP server failed to start with exit code $exit_code"
+        exit 1
+    fi
+}
+
+echo ""
+echo "=== All MCP smoke tests passed ==="