HTCP: Check for too-small packed and too-large unpacked fields (#2164)

HTCP: Check for too-small packed and too-large unpacked fields (#2164)

Harden HTCP parsing by checking HTCP fields

- Check packed field lengths and buffer space before reads.
- Guard CLR "reason" when sz < 2; log invalid messages.
- Support old minor==0 layout with safe prefix copy.
- Use early returns and unique_ptr for safer flows.