feat: add PDF CV read-only support + fix McpApplicationToolsTest - Add read_only flag to GoogleDriveBaseResume (V27 migration) - PDF files registered as base resumes are automatically read-only - PDF text extracted via Apache PDFBox 3.0.4 - Guards added: cannot copy/generate/detect-placeholders on read-only resumes - readOnly field propagated to all DTOs and MCP tool descriptions - Fix McpApplicationToolsTest: mock ToolMetricsCollector and delegate to supplier#49