feat: paginate, sync, and display branched sessions (#563)

* mobile: 以 Desktop Sessions 作为聊天历史源

* mobile: 修复快速连接崩溃与无标题会话隐藏

* mobile: 对齐 Desktop 标题并恢复完整历史

* mobile: 分离 Desktop 存储 ID 与运行 Session ID

* mobile: 将新对话持久化为 Desktop Session

* mobile: 渲染 Desktop 本地媒体

* feat: 分页加载并同步当前会话

* fix: 显示分支会话名称与层级

* fix: align PR with upstream app contract

* fix: preserve upstream session RPC lifecycle

app/src/test/java/com/m57/hermescontrol/data/model/SessionTreeTest.kt

@@ -0,0 +1,45 @@
+package com.m57.hermescontrol.data.model
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class SessionTreeTest {
+    @Test
+    fun nestsBranchesAndUsesDesktopFallbackNames() {
+        val sessions =
+            listOf(
+                SessionInfo(id = "unrelated", title = "Recent root"),
+                SessionInfo(id = "branch-b", parent_session_id = "parent"),
+                SessionInfo(id = "parent", title = "Original"),
+                SessionInfo(id = "branch-a", parent_session_id = "parent", preview = "copied prompt"),
+                SessionInfo(id = "nested", parent_session_id = "branch-a", title = "Named nested branch"),
+            )
+
+        val tree = flattenSessionTree(sessions)
+
+        assertEquals(listOf("unrelated", "parent", "branch-b", "branch-a", "nested"), tree.map { it.session.id })
+        assertEquals(listOf(0, 0, 1, 1, 2), tree.map { it.depth })
+        assertEquals(
+            listOf("Recent root", "Original", "branch 1", "branch 2", "Named nested branch"),
+            tree.map {
+                it.displayTitle
+            },
+        )
+        assertEquals(listOf(null, null, "├─", "└─", "└─"), tree.map { it.branchStem })
+    }
+
+    @Test
+    fun keepsMissingParentsAndCyclesVisible() {
+        val sessions =
+            listOf(
+                SessionInfo(id = "orphan", parent_session_id = "missing", preview = "orphan preview"),
+                SessionInfo(id = "a", parent_session_id = "b"),
+                SessionInfo(id = "b", parent_session_id = "a"),
+            )
+
+        val tree = flattenSessionTree(sessions)
+
+        assertEquals(setOf("orphan", "a", "b"), tree.map { it.session.id }.toSet())
+        assertEquals("orphan preview", tree.first { it.session.id == "orphan" }.displayTitle)
+    }
+}

app/src/test/java/com/m57/hermescontrol/data/remote/HermesApiServiceMockWebServerTest.kt

@@ -141,7 +141,8 @@ class HermesApiServiceMockWebServerTest {
                                     "created_at": "2026-06-20T14:30:00Z",
                                     "message_count": 7,
                                     "status": "idle",
-                                    "source": "web"
+                                    "source": "web",
+                                    "parent_session_id": "abc-123"
                                 }
                             ],
                             "total": 2,
@@ -173,6 +174,7 @@ class HermesApiServiceMockWebServerTest {
             assertEquals(7, second.message_count)
             assertEquals("idle", second.status)
             assertEquals("web", second.source)
+            assertEquals("abc-123", second.parent_session_id)
         }
 
     @Test
@@ -254,6 +256,24 @@ class HermesApiServiceMockWebServerTest {
             assertEquals("tool_execution", messages[2].type)
         }
 
+    @Test
+    fun getSessionMessages_sendsPaginationQuery() =
+        runBlocking {
+            mockServer.enqueue(
+                MockResponse()
+                    .setResponseCode(200)
+                    .setBody("{\"messages\": []}"),
+            )
+
+            val response = api.getSessionMessages("desktop/session", limit = 150, offset = 300)
+
+            assertTrue(response.isSuccessful)
+            assertEquals(
+                "/api/sessions/desktop/session/messages?limit=150&offset=300",
+                mockServer.takeRequest().path,
+            )
+        }
+
     @Test
     fun getSessionMessages_withNullRole_doesNotCrash() =
         runBlocking {