Addresses two findings in commit 762fd42 review:
1. BUG: guard query was tautological. `SELECT MAX(number) FROM prs WHERE
number < 900000` filters out exactly what the `>= 900000` check tests.
Replaced with a direct check for unexpected rows in the synthetic range
(excluding our known 900068/900088).
2. WARNING: origin defaults to 'pipeline' via schema default. lib/merge.py
convention is origin='human' for external contributors. Synthetic rows
now set origin='human', priority='high' — matches discover_external_prs
for real GitHub PRs. Prevents Phase B origin-based filtering from
misclassifying Alex/Cameron as machine-authored.
Also flagged in review: credit projection was optimistic. Author events are
PR-level (not per-claim), so Alex gets 1×0.30 author credit, not 6. Same
for Cameron. Per-claim originator credit goes to the 7 frontmatter sourcers
where applicable. Not a code change — expectation reset for Cory.
m3taversal
0f2b153c92