topdata: stop hardcoding the skills dataset location

The skills dataset moved into a tree (skills/core, skills/specs, ...).
Resolve it data-driven instead of by name:

- The required-family check no longer pins skill focus families to
  dataset "skills"; the family spec's child_source names the dataset.
- Affinity generation and display names use the skill_focus spec's
  child_source dataset.
- Child slugs derive from the row key's own namespace (text after the
  first colon) instead of assuming namespace == dataset path.
- The wiki loader accepts both layouts ("skills", then "skills/core").

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/topdata/wiki_native.go

@@ -569,11 +569,13 @@ func loadWikiContext(dataDir, sourceDir string) (*wikiContext, error) {
 	if err != nil {
 		return nil, err
 	}
-	loadBase := func(name string) (nativeCollectedDataset, bool, error) {
-		for _, dataset := range datasets {
-			if dataset.Name == name {
-				collected, err := collectNativeDataset(dataset)
-				return collected, true, err
+	loadBase := func(names ...string) (nativeCollectedDataset, bool, error) {
+		for _, name := range names {
+			for _, dataset := range datasets {
+				if dataset.Name == name {
+					collected, err := collectNativeDataset(dataset)
+					return collected, true, err
+				}
 			}
 		}
 		return nativeCollectedDataset{}, false, nil
@@ -583,7 +585,7 @@ func loadWikiContext(dataDir, sourceDir string) (*wikiContext, error) {
 	if err != nil {
 		return nil, err
 	}
-	skillDataset, skillOK, err := loadBase("skills")
+	skillDataset, skillOK, err := loadBase("skills", "skills/core")
 	if err != nil {
 		return nil, err
 	}