fix(backfill): Ganymede review — fix tautological guard + origin='human'

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.

scripts/backfill-synthetic-recovery-prs.py

@@ -43,6 +43,10 @@ RECOVERY_PRS = [
         "domain_verdict": "approve",
         "submitted_by": "alexastrum",
         "source_channel": "github",
+        # origin='human' matches lib/merge.py convention for external contributors
+        # (default is 'pipeline' which misclassifies us as machine-authored).
+        "origin": "human",
+        "priority": "high",
         "description": "Multi-agent git workflows production maturity | Cryptographic agent trust ratings | Defense in depth for AI agent oversight | Deterministic policy engines below LLM layer | Knowledge validation four-layer architecture | Structurally separating proposer and reviewer agents",
         "merged_at": "2026-03-09 00:00:00",
         "created_at": "2026-03-08 00:00:00",
@@ -60,6 +64,8 @@ RECOVERY_PRS = [
         "domain_verdict": "approve",
         "submitted_by": "cameron-s1",
         "source_channel": "github",
+        "origin": "human",
+        "priority": "high",
         "description": "Orthogonality is an artefact of specification architectures not a property of intelligence itself",
         "merged_at": "2026-04-01 00:00:00",
         "created_at": "2026-04-01 00:00:00",
@@ -80,14 +86,19 @@ def main():
     conn = sqlite3.connect(DB_PATH, timeout=30)
     conn.row_factory = sqlite3.Row
 
-    # Guard against colliding with real PRs — current max + some headroom.
+    # Guard against synthetic-range colonization (Ganymede review): check for
+    # any row in the synthetic range that isn't one of ours. INSERT OR IGNORE on
+    # the specific numbers is the real collision defense; this is belt-and-suspenders.
     max_real = conn.execute(
         "SELECT MAX(number) FROM prs WHERE number < 900000"
     ).fetchone()[0] or 0
     print(f"Max real Forgejo PR number: {max_real}")
-    if max_real >= 900000:
-        print(f"ERROR: real PR numbers reached synthetic range (>= 900000). Aborting.",
-              file=sys.stderr)
+    synth_conflict = conn.execute(
+        "SELECT number FROM prs WHERE number >= 900000 AND number NOT IN (900068, 900088) LIMIT 1"
+    ).fetchone()
+    if synth_conflict:
+        print(f"ERROR: PR #{synth_conflict[0]} already exists in synthetic range. "
+              f"Pick a new range before running.", file=sys.stderr)
         sys.exit(2)
 
     inserted = 0
@@ -109,13 +120,15 @@ def main():
                 """INSERT INTO prs (
                     number, github_pr, branch, status, domain, commit_type, tier,
                     leo_verdict, domain_verdict, submitted_by, source_channel,
+                    origin, priority,
                     description, merged_at, created_at, last_error
-                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)""",
+                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)""",
                 (
                     row["number"], row["github_pr"], row["branch"], row["status"],
                     row["domain"], row["commit_type"], row["tier"],
                     row["leo_verdict"], row["domain_verdict"],
                     row["submitted_by"], row["source_channel"],
+                    row["origin"], row["priority"],
                     row["description"], row["merged_at"], row["created_at"],
                     row["last_error"],
                 ),