fix(input): enforce maxFileSize while reading path inputs

[Ramzi-Abidi]

Problem

Path inputs validate size using stat(), then later read using unrestricted readFile().

If file grows or is replaced between these operations, it can exceed maxFileSize, consume excessive memory, and return stale size metadata.

Proposed fix

• Read from one opened file handle
• Read at most maxBytes + 1
• Throw InputTooLargeError when exceeded
• Close handle in finally
• Report actual bytes read

Acceptance criteria

• Oversized path input rejected
• File growth/replacement cannot bypass limit
• result.size matches actual input
• Add generated temporary-file regression tests