fix(python): parse empty trigram/vector ranks in hachimoji_citation

Empty ranks from FULL OUTER JOIN return empty strings, not '0'.  Fixed
int() parsing to handle empty fields. Now regime clustering is verified:
- Φ queries retrieve phase transition papers
- Ω queries retrieve critical/eigensolid papers

Build: 2987 jobs, 0 errors (lake build)

python/hachimoji_citation.py

@@ -272,11 +272,13 @@ def cite_equation(
             parts = line.split("|")
             if len(parts) >= 5:
                 try:
+                    trig = int(parts[2]) if parts[2].strip() else 0
+                    vec = int(parts[3]) if parts[3].strip() else 0
                     citations.append(Citation(
                         paper_id     = parts[0].strip(),
                         title        = parts[1].strip()[:200],
-                        trigram_rank = int(parts[2].strip()),
+                        trigram_rank = trig,
-                        vector_rank  = int(parts[3].strip()),
+                        vector_rank  = vec,
                         rrf_score    = float(parts[4].strip()),
                     ))
                 except (ValueError, IndexError):
@@ -338,10 +340,12 @@ def cite_batch(
             parts = line.split("|")
             if len(parts) >= 5:
                 try:
+                    trig = int(parts[2]) if parts[2].strip() else 0
+                    vec = int(parts[3]) if parts[3].strip() else 0
                     citations.append(Citation(
                         paper_id=parts[0].strip(), title=parts[1].strip()[:200],
-                        trigram_rank=int(parts[2].strip()),
+                        trigram_rank=trig,
-                        vector_rank=int(parts[3].strip()),
+                        vector_rank=vec,
                         rrf_score=float(parts[4].strip()),
                     ))
                 except (ValueError, IndexError):