Creating a pull request for a finished run read the projection's final
patch field directly. Petri stores that patch in the blob table and the
field holds a blob reference, so the description model was handed the
reference string instead of the diff, and the empty-diff check could
never fire.
Move the reference resolution out of Files Changed into a shared
final_patch::load helper and use it for both readers. Pull request input
extraction now reads the real patch, judges emptiness by its text, and
reports a missing or unreadable blob instead of describing a placeholder.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
