Publish leadership appearance backfill - #13

Summary

• merge 28 editorially accepted founder and executive appearances into the main appearances chronology
• remove the separate public backfill page and queue artifact
• retain all 31 reviewed candidates in an append-only audit run with exact capture evidence and three documented rejections

Validation

• bun test (123 passed)
• bun run history:research:audit -- --capture-root
• bun run typecheck
• bun run lint
• bun run build
• git diff --check