Aligned the runtime header parser with the formal grammar's no-`#`-in-filename rule: any `#` left in the path body after detecting the trailing `#XXXX` tag means the header is malformed (short `#1A2`, non-hex `#1A2G`, over-long `#1A2B5`, stale-tag copy-paste, line-suffixed tags), not a path with an embedded hash. Mirrored the same rule on the apply_patch recovery path.
Added strict and recovery regression coverage for the three malformed-tag shapes the reviewer named.
roboomp
7fcdfd048f