Parser: chained .replace() calls processed \n before \\, causing \\n
to become a real newline. Replaced with character-by-character
_unescape_string. Fixes 2 parser spec test failures.
Primitives: prim_get only handled dict and list. Objects with .get()
methods (like PageDef) returned None. Added hasattr fallback.
Fixes 9 defpage spec test failures.
All 259 spec tests now pass (was 244/259).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>