fix: update integration tests to use valid tools after v2.25.0 removal

Replaced all references to removed tools in integration tests:
- list_nodes -> search_nodes
- get_database_statistics -> tools_documentation
- list_ai_tools -> search_nodes/tools_documentation
- list_tasks -> tools_documentation
- get_node_as_tool_info -> removed test section

Updated test files:
- tests/integration/mcp-protocol/basic-connection.test.ts
- tests/integration/mcp-protocol/performance.test.ts
- tests/integration/mcp-protocol/session-management.test.ts
- tests/integration/mcp-protocol/test-helpers.ts
- tests/integration/mcp-protocol/tool-invocation.test.ts
- tests/integration/telemetry/mcp-telemetry.test.ts
- tests/unit/mcp/disabled-tools.test.ts
- tests/unit/mcp/tools-documentation.test.ts

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/integration/mcp-protocol/test-helpers.ts

@@ -114,7 +114,7 @@ export class TestableN8NMCPServer {
     // The MCP server initializes its database lazily
     // We can trigger initialization by calling executeTool
     try {
-      await this.mcpServer.executeTool('get_database_statistics', {});
+      await this.mcpServer.executeTool('tools_documentation', {});
     } catch (error) {
       // Ignore errors, we just want to trigger initialization
     }