Drop stale evidence when the walkthrough seed is re-run

Evidence rows are keyed on the filename, so reassigning the in-flight batch's
intakes left the old harvest_document row behind. Delete anything the case no
longer references, mirroring the lineage cleanup in _batch.

apps/core/management/commands/seed_walkthrough.py

@@ -173,7 +173,15 @@ class Command(BaseCommand):
 
     # --------------------------------------------------------------------- steps
 
-    def _origin_chain(self, verifier: User) -> tuple[OriginZone, list[HarvestIntake]]:
+    def _origin_chain(self, verifier: User) -> tuple[OriginZone, list[HarvestIntake], list[HarvestIntake]]:
+        """The zone, the groups, and two separate sets of harvest intakes.
+
+        Two sets, not one, because an intake is a finite quantity of shea: the
+        completed batch and the in-flight batch each consume their own material.
+        The command used to hand the same three intakes to both batches, which
+        allocated 800 kg of an 820 kg intake twice over — invisible until the ops
+        portal grew a lineage screen that refuses exactly that.
+        """
         facility, _ = Facility.objects.update_or_create(
             name="IXG Processing Facility - Katsina",
             defaults={
@@ -228,7 +236,13 @@ class Command(BaseCommand):
             ("IXG-INTAKE-2026-0142", group_a, date(2026, 8, 27), Decimal("640.00"), "A"),
             ("IXG-INTAKE-2026-0143", group_b, date(2026, 8, 29), Decimal("600.00"), "B"),
         ]
-        for ref, group, when, weight, grade in intake_specs:
+        # The in-flight batch's own material, delivered the following week.
+        inflight_specs = [
+            ("IXG-INTAKE-2026-0144", group_a, date(2026, 8, 30), Decimal("560.00"), "A"),
+            ("IXG-INTAKE-2026-0145", group_b, date(2026, 9, 1), Decimal("540.00"), "A"),
+            ("IXG-INTAKE-2026-0146", group_b, date(2026, 9, 3), Decimal("460.00"), "B"),
+        ]
+        for ref, group, when, weight, grade in intake_specs + inflight_specs:
             intake, _ = HarvestIntake.objects.update_or_create(
                 intake_reference=ref,
                 defaults={
@@ -243,20 +257,27 @@ class Command(BaseCommand):
                 },
             )
             intakes.append(intake)
-        return zone, intakes
+        return zone, intakes[: len(intake_specs)], intakes[len(intake_specs):]
 
     def _batch(self, ref: str, intakes: list[HarvestIntake], enterer: User, **fields) -> ProcessingBatch:
+        allocations = fields.pop("allocations", [Decimal("800.00"), Decimal("640.00"), Decimal("560.00")])
         batch, created = ProcessingBatch.objects.update_or_create(
             batch_reference=ref,
             defaults={"origin_facility": "ASI - Katsina State, Nigeria", "created_by": enterer, **fields},
         )
-        allocations = [Decimal("800.00"), Decimal("640.00"), Decimal("560.00")]
         for intake, weight in zip(intakes, allocations):
             IntakeBatchLineage.objects.update_or_create(
                 batch=batch,
                 harvest_intake=intake,
                 defaults={"weight_allocated_kg": weight},
             )
+        # ...and drop anything this batch used to be linked to. Without this the
+        # command is only idempotent while the chain does not change: re-running it
+        # after a change leaves the old links in place, which is how both demo
+        # batches came to be traced back to the same three intakes.
+        IntakeBatchLineage.objects.filter(batch=batch).exclude(
+            harvest_intake__in=[i.pk for i in intakes]
+        ).delete()
         return batch
 
     def _qc(self, batch: ProcessingBatch, enterer: User, verifier: User, spec: ProductSpecification | None) -> QCResult:
@@ -495,11 +516,17 @@ class Command(BaseCommand):
             },
         )
 
+        evidence_files = [
+            f"{zone.zone_code}-geolocation.json",
+            f"{intakes[0].intake_reference}-weighbridge-ticket.pdf",
+            "collector-group-register.pdf",
+            "export-permit-and-land-use.pdf",
+        ]
         for etype, name in (
-            (EUDREvidence.EvidenceType.GEOLOCATION, f"{zone.zone_code}-geolocation.json"),
+            (EUDREvidence.EvidenceType.GEOLOCATION, evidence_files[0]),
-            (EUDREvidence.EvidenceType.HARVEST_DOCUMENT, f"{intakes[0].intake_reference}-weighbridge-ticket.pdf"),
+            (EUDREvidence.EvidenceType.HARVEST_DOCUMENT, evidence_files[1]),
-            (EUDREvidence.EvidenceType.SUPPLIER_IDENTITY, "collector-group-register.pdf"),
+            (EUDREvidence.EvidenceType.SUPPLIER_IDENTITY, evidence_files[2]),
-            (EUDREvidence.EvidenceType.LEGALITY, "export-permit-and-land-use.pdf"),
+            (EUDREvidence.EvidenceType.LEGALITY, evidence_files[3]),
         ):
             EUDREvidence.objects.update_or_create(
                 case=case, evidence_type=etype, file=name,
@@ -511,6 +538,12 @@ class Command(BaseCommand):
                     "notes": "Synthetic evidence record for training.",
                 },
             )
+        # ...and drop anything this case used to carry. Evidence is keyed on the
+        # filename, so reassigning the batch's intakes leaves the old
+        # harvest_document row behind. Mirrors the lineage cleanup in _batch.
+        EUDREvidence.objects.filter(case=case).exclude(
+            file__in=evidence_files
+        ).delete()
 
         RiskAssessment.objects.update_or_create(
             case=case, risk_level=DueDiligenceCase.RiskLevel.LOW,
@@ -616,8 +649,12 @@ class Command(BaseCommand):
             self.stderr.write("No ops user found - create one before seeding.")
             return
 
-        zone, intakes = self._origin_chain(verifier or enterer)
+        zone, intakes, inflight_intakes = self._origin_chain(verifier or enterer)
-        self.stdout.write(f"  origin:       {zone.zone_code}, {len(intakes)} harvest intakes")
+        self.stdout.write(
+            f"  origin:       {zone.zone_code}, "
+            f"{len(intakes) + len(inflight_intakes)} harvest intakes "
+            f"({len(intakes)} for {COMPLETED_BATCH}, {len(inflight_intakes)} for {INFLIGHT_BATCH})"
+        )
 
         # 1. completed happy path
         completed = self._batch(
@@ -636,9 +673,11 @@ class Command(BaseCommand):
         ])
         self.stdout.write(f"  {COMPLETED_BATCH}: delivered, QC pass, CoA published ({coa.sha256_hash[:12]}...), EUDR approved")
 
-        # 2. mid-flight
+        # 2. mid-flight. Its own intakes: three intakes cannot be allocated into
+        #    two batches, and the lineage screen would refuse to save that.
         inflight = self._batch(
-            INFLIGHT_BATCH, intakes, enterer,
+            INFLIGHT_BATCH, inflight_intakes, enterer,
+            allocations=[Decimal("540.00"), Decimal("520.00"), Decimal("440.00")],
             harvest_date=date(2026, 9, 4), weight_kg=Decimal("1500.00"),
             grade=ProcessingBatch.Grade.B, status=ProcessingBatch.Status.IN_TRANSIT,
             notes="Synthetic batch currently in transit - used to show work in progress.",
@@ -646,7 +685,7 @@ class Command(BaseCommand):
         qc2 = self._qc(inflight, enterer, verifier or enterer, spec)
         self._documents(inflight, qc2, enterer, verifier or enterer, date(2026, 9, 10),
                         is_completed=False, coa_published=False)
-        self._eudr(inflight, zone, intakes, enterer, verifier or enterer, approved=False)
+        self._eudr(inflight, zone, inflight_intakes, enterer, verifier or enterer, approved=False)
         self._shipment(inflight, delivered=False)
         self._esg(inflight, [(date(2026, 9, 6), 27, 16, "Synthetic report: intake day observations.")])
         self.stdout.write(f"  {INFLIGHT_BATCH}: in transit, CoA awaiting release, EUDR complete for review")