perf(home): @Immutable on HomeAction/PendingActionCard/HomeCategorySummary

Part 2b (Compose stack advantage). Marks the three verified-deeply-immutable
card models @Immutable so their single-instance params get structural-equality
skipping (upgrade over the K2 reference-equality strong-skipping default).
HomeAnswerStats/HomeUiState left unannotated (LocalAnswer/Question/Set transitive
types not fully audited — a false @Immutable promise would cause stale UI).
Rendered output identical; only recomposition frequency drops. compile green.

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

app/src/main/java/app/closer/ui/home/HomeModels.kt

@@ -1,5 +1,6 @@
 package app.closer.ui.home
 
+import androidx.compose.runtime.Immutable
 import app.closer.core.navigation.AppRoute
 import app.closer.domain.model.GameType
 import app.closer.domain.model.LocalAnswer
@@ -13,6 +14,9 @@ import app.closer.domain.model.QuestionCategory
  * ViewModel. Behavior-identical to the originals.
  */
 
+// @Immutable: deeply immutable (QuestionCategory is all String vals) → structural-equality skipping
+// for the category cards, an upgrade over the reference-equality strong-skipping default.
+@Immutable
 data class HomeCategorySummary(
     val category: QuestionCategory,
     val questionCount: Int
@@ -52,6 +56,9 @@ enum class HomeActionTone {
     Pending
 }
 
+// @Immutable: only String/enum/primitive fields → the single-instance card params
+// (primaryAction, secondary/feed items) become value-skippable.
+@Immutable
 data class HomeAction(
     val eyebrow: String,
     val title: String,
@@ -66,6 +73,8 @@ data class HomeAction(
     val gameRoute: String? = null
 )
 
+// @Immutable: only String/Int/enum fields → the pending-card params become value-skippable.
+@Immutable
 data class PendingActionCard(
     val title: String,
     val subtitle: String?,