feat: expose list file filters

[jlitola]

Summary

• expose the backend listRepoFiles v7 filter surface through the code_files MCP tool and the githits code files CLI command
• forward selector, extension, language, file type, and file-intent filters through shared request building and the code navigation service
• extend parity, request-builder, response, text-format, and CLI tests to lock the new filter behavior on both surfaces

Verification

• bun test src/shared/list-files-request.test.ts src/shared/list-files-response.test.ts src/shared/list-files-text.test.ts src/tools/list-files.test.ts src/tools/list-files-parity.test.ts src/commands/code/files.test.ts src/services/code-navigation-service.test.ts src/commands/mcp-instructions.test.ts
• bun run build