fix: preserve CRLF namespace byte offsets

[vycdev2]

Summary

• compute namespace pre-scan offsets from each line segment’s actual byte length so CRLF input does not drift
• add a regression covering multiple namespace declarations in a CRLF source file

Verification

• cargo test -q -p jett_project — passed: 8 tests
• cargo build — passed
• cargo test -q — passed
• cargo fmt --check — passed
• git diff --check — passed

Risk

• Low: the change is limited to the private namespace pre-scan line iterator and preserves LF behavior while accounting for CRLF byte width.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.