The structural token lexer was already fully implemented. All 84 lexer
tests pass, covering all acceptance criteria:
- Array/dict delimiters ([], <<>>)
- Keywords (true, false, null, obj, endobj, stream, endstream, R)
- Hex string vs dict ambiguity (< vs <<)
- Stream header validation (\n or \r\n only, lone \r is invalid)
- Case-sensitive keyword matching
This commit fixes a pre-existing compilation error in xref.rs where
forward_scan_memory() called parse_obj_header_at_memory() which didn't
exist. Added the missing function as a byte-slice variant of
parse_obj_header_at() for efficient memory-based scanning.
Verification: notes/pdftract-5upi.md
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
a88353069a