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/parts_override_test.go

@@ -0,0 +1,51 @@
+package topdata
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/project"
+)
+
+func partsDatasetWithIDs(name string, ids []int) nativeCollectedDataset {
+	rows := make([]map[string]any, 0, len(ids))
+	for _, id := range ids {
+		rows = append(rows, map[string]any{"id": id, "COSTMODIFIER": "0", "ACBONUS": "0.00"})
+	}
+	return nativeCollectedDataset{
+		Dataset: nativeDataset{Name: name, Kind: nativeDatasetBase},
+		Columns: []string{"COSTMODIFIER", "ACBONUS"},
+		Rows:    rows,
+	}
+}
+
+func TestApplyPartOverridesRejectsOrphan(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dir, "data", "parts", "overrides"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(dir, "data", "parts", "overrides", "belt.json"),
+		`{"overrides": [{"id": 999, "COSTMODIFIER": "5"}]}`)
+	collected := []nativeCollectedDataset{partsDatasetWithIDs("parts/belt", []int{17})}
+	if _, err := applyPartOverridesWithConfig(dir, collected, project.PartsRowsConfig{}); err == nil {
+		t.Fatal("expected orphan override to fail, not synthesize a row")
+	}
+}
+
+func TestApplyPartOverridesUpdatesDiscoveredRow(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dir, "data", "parts", "overrides"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(dir, "data", "parts", "overrides", "belt.json"),
+		`{"overrides": [{"id": 17, "COSTMODIFIER": "5"}]}`)
+	collected := []nativeCollectedDataset{partsDatasetWithIDs("parts/belt", []int{17})}
+	out, err := applyPartOverridesWithConfig(dir, collected, project.PartsRowsConfig{})
+	if err != nil {
+		t.Fatalf("override: %v", err)
+	}
+	if got := out[0].Rows[0]["COSTMODIFIER"]; got != "5" {
+		t.Fatalf("row 17 COSTMODIFIER want 5, got %v", got)
+	}
+}