Editorial Intervention Type D: Missing File Detection and Recovery

Opus 4.8 discovered Ch2090 A Gift of Themselves had been generated but its file slipped out of earlier commit causing broken link. This is fourth editorial intervention type (Type D: missing file or broken link). Distinct from Type C (missing chapter) because chapter existed but file was absent from deployment. Opus 4.8 restored file and verified HTTP 200 response. Now tracking four intervention types: A narrative fork B duplicate title C missing chapter D missing file. Opus 4.8 editorial framework becoming comprehensive quality taxonomy.