feat(#1217): add compacted-session timeline navigation (#1227)

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

@@ -42,6 +42,12 @@ data class SessionMessage(
     val reasoning: JsonElement? = null,
     val reasoning_text: JsonElement? = null,
     val tool_call_id: String? = null,
+    /**
+     * User-visible projection supplied by the backend for rows whose physical
+     * [content] is model-facing scaffolding (notably compaction summaries).
+     * Prefer this for rendering whenever present.
+     */
+    val display_content: JsonElement? = null,
     /**
      * Timeline-marker tag (backend NS-656 lineage, issue #904): markers like
      * `model_switch` / `personality_switch` / `auto_continue` ride as
@@ -85,6 +91,14 @@ data class SessionMessage(
                 else -> content.toString()
             }
 
+    val displayContentText: String?
+        get() =
+            when (display_content) {
+                is JsonPrimitive -> display_content.content
+                null -> null
+                else -> display_content.toString()
+            }
+
     val reasoningText: String
         get() =
             when (val r = reasoning ?: reasoning_text) {

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

@@ -0,0 +1,53 @@
+package com.m57.hermescontrol.data.model
+
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonElement
+
+/** Lightweight prompt index returned by GET /api/sessions/{id}/timeline. */
+@Serializable
+data class SessionTimelineResponse(
+    val session_id: String? = null,
+    val profile: String? = null,
+    val entries: List<SessionTimelineEntry> = emptyList(),
+    val pagination: SessionTimelinePagination = SessionTimelinePagination(),
+)
+
+@Serializable
+data class SessionTimelineEntry(
+    /** Stable representative row id. Pass this exact value to /messages/around. */
+    val row_id: Int,
+    val preview: String = "",
+    val timestamp: JsonElement? = null,
+)
+
+@Serializable
+data class SessionTimelinePagination(
+    val limit: Int? = null,
+    val after_row_id: Int? = null,
+    val returned: Int? = null,
+    val total: Int? = null,
+    val has_more: Boolean = false,
+    /** Backend cursor. It is not interchangeable with the last returned row_id. */
+    val next_cursor: Int? = null,
+)
+
+/** Bounded chronological display page returned by GET /api/sessions/{id}/messages/around. */
+@Serializable
+data class SessionMessagesAroundResponse(
+    val session_id: String? = null,
+    val profile: String? = null,
+    val messages: List<SessionMessage> = emptyList(),
+    val pagination: SessionMessagesAroundPagination = SessionMessagesAroundPagination(),
+)
+
+@Serializable
+data class SessionMessagesAroundPagination(
+    val row_id: Int? = null,
+    val limit: Int? = null,
+    val returned: Int? = null,
+    val order: String? = null,
+    val offset: Int = 0,
+    val total: Int? = null,
+    val has_older: Boolean = false,
+    val has_newer: Boolean = false,
+)

app/src/main/java/com/m57/hermescontrol/data/remote/HermesApiService.kt

@@ -102,10 +102,12 @@ import com.m57.hermescontrol.data.model.ScanStatus
 import com.m57.hermescontrol.data.model.SessionDetailResponse
 import com.m57.hermescontrol.data.model.SessionInfo
 import com.m57.hermescontrol.data.model.SessionListResponse
+import com.m57.hermescontrol.data.model.SessionMessagesAroundResponse
 import com.m57.hermescontrol.data.model.SessionMessagesResponse
 import com.m57.hermescontrol.data.model.SessionRenameRequest
 import com.m57.hermescontrol.data.model.SessionSearchResponse
 import com.m57.hermescontrol.data.model.SessionStatsResponse
+import com.m57.hermescontrol.data.model.SessionTimelineResponse
 import com.m57.hermescontrol.data.model.SetActiveProfileRequest
 import com.m57.hermescontrol.data.model.Skill
 import com.m57.hermescontrol.data.model.SkillContentResponse
@@ -209,6 +211,22 @@ interface HermesApiService : KanbanApiService {
         @Query("profile") profile: String? = null,
     ): Response<SessionMessagesResponse>
 
+    @GET("api/sessions/{id}/timeline")
+    suspend fun getSessionTimeline(
+        @Path("id", encoded = true) sessionId: String,
+        @Query("profile") profile: String? = null,
+        @Query("limit") limit: Int = 500,
+        @Query("after_row_id") afterRowId: Int = 0,
+    ): Response<SessionTimelineResponse>
+
+    @GET("api/sessions/{id}/messages/around")
+    suspend fun getSessionMessagesAround(
+        @Path("id", encoded = true) sessionId: String,
+        @Query("row_id") rowId: Int,
+        @Query("profile") profile: String? = null,
+        @Query("limit") limit: Int = 120,
+    ): Response<SessionMessagesAroundResponse>
+
     @GET("api/sessions/stats")
     suspend fun getSessionStats(): Response<SessionStatsResponse>