GHSA-hwpp-h97w-2h3j: repomix: attach_packed_output can bypass file-read secret scanning for supported local files

Repomix's MCP server (a protocol for connecting AI assistants to tools) has a security weakness where the `attach_packed_output` function can register arbitrary local files with certain extensions (.json, .txt, .md, .xml) and bypass the secret-scanning check that normally blocks sensitive files from being read. An attacker using MCP tools can register any supported file type as output, get an ID for it, then use `read_repomix_output` to read the full file content without the safety check being applied.