feat(chat/activity): Self-improvement event badges for memory & skill updates (#744)

* feat(chat/activity): Self-improvement event badges for memory & skill updates (#737)

* feat(chat): Handle background review.summary WS events for self-improvement notices

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/model/LearningGraphModels.kt

@@ -0,0 +1,42 @@
+package com.m57.hermescontrol.data.model
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/**
+ * Data structures for the Hermes agent self-improvement / learning graph endpoint
+ * GET /api/learning/graph
+ */
+@Serializable
+data class LearningGraphNode(
+    val id: String,
+    val label: String,
+    val kind: String, // "skill" | "memory"
+    val timestamp: Long? = null,
+    val category: String? = null,
+    @SerialName("useCount") val useCount: Int = 0,
+    val state: String? = null,
+    @SerialName("createdBy") val createdBy: String? = null,
+    val pinned: Boolean = false,
+)
+
+@Serializable
+data class LearningGraphEdge(
+    val source: String,
+    val target: String,
+)
+
+@Serializable
+data class LearningGraphMemoryCard(
+    val source: String,
+    val timestamp: Long? = null,
+    val title: String,
+    val body: String,
+)
+
+@Serializable
+data class LearningGraphResponse(
+    val nodes: List<LearningGraphNode> = emptyList(),
+    val edges: List<LearningGraphEdge> = emptyList(),
+    val memory: List<LearningGraphMemoryCard> = emptyList(),
+)