Warn when masterfeat expansion silently drops unobtainable feats

classFeatExpansionCanUseFeat excludes ALLCLASSESCANUSE=0 feats from
class feat table masterfeat expansion. When such a feat also has no
MinLevelClass, no class can ever obtain it — a data bug that previously
failed silently (e.g. Spell Focus vanishing from the wizard table).

New validator warns for exactly that case; deliberate exclusions with
an explicit MinLevelClass stay silent.

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

internal/topdata/topdata.go

@@ -268,6 +268,7 @@ func ValidateProject(p *project.Project) ValidationReport {
 	validateNativeLockAllocation(dataDir, p.EffectiveConfig().TopData.RowGeneration, &report)
 	validateGeneratedFeatFamilies(dataDir, &report)
 	validateClassSpellbooks(dataDir, &report)
+	validateClassFeatMasterfeatAccessibility(dataDir, &report)
 	validateItempropsRegistryGraph(dataDir, &report)
 	if _, err := os.Stat(statePath); err == nil {
 		report.Files++