PoC for schema.ParseFile file-descriptor leak

This PoC repeatedly calls schema.ParseFile on a valid schema file. Because
ParseFile opens the file but never closes it, open file descriptors accumulate
until the process hits its file descriptor limit and fails with "too many open files".

Reproduction steps (from repo root):
1. Ensure Go module dependencies are available (offline builds need a populated
   module cache or vendored deps).
2. Run with a low ulimit and GC disabled so file descriptors are not reclaimed:
   
   /bin/sh -c 'ulimit -n 256; GOGC=off go run leak_poc.go'

Expected result:
- The program prints increasing fd counts and panics with an error like:
  "iteration N: open schema/v1.0/testdata/valid-example.yaml: too many open files"

Notes:
- If dependencies are not available offline, pre-fetch or vendor them before running.
