feat(topdata): parts autogen from CDN part.yml channel

Phase 2 of the parts-row autogen design: Crucible resolves parts 2DA rows
from the immutable part.yml published with the asset HAK release, over the
anonymous Bunny CDN channel, with the parts consumer required (no fail-open).

- generalize resolveCDNChannelManifest: derive manifest basename + provenance
  label from config; drop hardcoded assets/vfxs.yml so part.yml resolves too
- add filterPartsCDNChannelEntries + mode dispatch implementing the inventory
  contract (restype mdl under part/<cat>/, trailing-digit row id, dedup
  l/r/race/gender variants, sort by source, zero accepted rows = hard fail)
- support hand category + parts/hand dataset mapping (12 datasets total)
- native pipeline: single augment -> normalize -> override sequence with the
  configured parts_rows policy; overrides may update but never synthesize a row
- reject multiple parts_rows consumers in project validation
- tests: parts filter contract, category coverage, offline basename, orphan
  override reject, and a parity guard proving a bare CDN-only parts build

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/topdata/parity_guard_test.go

@@ -1,6 +1,8 @@
 package topdata
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
 	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/project"
@@ -54,3 +56,45 @@ func TestParityGuardCDNChannelProducesAccessoryRows(t *testing.T) {
 		t.Fatalf("PARITY GUARD: expected lock id for %s, got %#v", wantKey, got[0].LockData)
 	}
 }
+
+// PARITY GUARD (parts): a bare project whose only parts source is the offline
+// CDN-equivalent (SOW_PART_MANIFEST -> a part.yml), with no NWN_ROOT, no token,
+// no asset checkout, must produce parts rows from the filtered inventory. If
+// parts resolution ever drifts back into a wrapper, this fails.
+func TestParityGuardCDNChannelProducesPartsRows(t *testing.T) {
+	root := testProjectRoot(t)
+	checkout := filepath.Join(root, "manifest-checkout")
+	if err := os.MkdirAll(filepath.Join(checkout, "assets"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(checkout, "assets", "part.yml"),
+		"assets:\n  - {path: part/belt/m/pfa0_belt017.mdl, restype: mdl}\n  - {path: part/belt/m/pfa0_belt018.mdl, restype: mdl}\n")
+	t.Setenv("SOW_PART_MANIFEST", checkout)
+	t.Setenv("NWN_ROOT", "")
+
+	c := projectPartsConsumer()
+	c.Source = project.AutogenSourceConfig{
+		Kind:               "cdn_channel",
+		ChannelsPath:       "releases/haks/channels.json",
+		ManifestPath:       "releases/haks/{tag}/part.yml",
+		ReleaseMarkerPath:  "releases/haks/{tag}/haks.json",
+		OfflineOverrideEnv: "SOW_PART_MANIFEST",
+	}
+
+	p := testProject(root)
+	p.Config.Autogen.Consumers = []project.AutogenConsumerConfig{c}
+
+	collected := []nativeCollectedDataset{partsDatasetWithIDs("parts/belt", nil)}
+
+	got, err := applyAutogenConsumers(p, collected, nil)
+	if err != nil {
+		t.Fatalf("applyAutogenConsumers failed: %v", err)
+	}
+	ids := map[int]bool{}
+	for _, row := range got[0].Rows {
+		ids[row["id"].(int)] = true
+	}
+	if !ids[17] || !ids[18] {
+		t.Fatalf("PARITY GUARD: expected belt rows 17 and 18 from inventory, got %#v", got[0].Rows)
+	}
+}