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/project/project.go

@@ -1581,6 +1581,15 @@ func validateAutogenConfig(cfg AutogenConfig) []error {
 
 func validateAutogenConsumerSources(consumers []AutogenConsumerConfig) []error {
 	var failures []error
+	partsRows := 0
+	for _, c := range consumers {
+		if strings.TrimSpace(c.Mode) == "parts_rows" {
+			partsRows++
+		}
+	}
+	if partsRows > 1 {
+		failures = append(failures, fmt.Errorf("at most one autogen consumer may use mode parts_rows; found %d (override precedence would be ambiguous)", partsRows))
+	}
 	for _, c := range consumers {
 		if strings.TrimSpace(c.Source.Kind) != "cdn_channel" {
 			continue