feat: 初始化 Android 客户端（M0 骨架 + M1 登录 + M2 基础模块）

M0：Gradle 9.7.1 / AGP 9.2.1 / Kotlin 2.4 / Miuix 0.9.3，minSdk 33，compileSdk 37。
M1：登录页（服务器地址可配、服务端/本地错误分流、EncryptedSharedPreferences、自动登录与静默重登、401 登出）。
M2 基础模块：消息内容解析器（<p>/<action>/<narration> + 流式增量）、WebSocket 客户端、REST 数据层与分页去重。
45 个单元测试全绿，真机验证通过（登录页 + 启动图标）。
devdocs/ 收录设计文档、前后端协同事项与细化方案。

app/src/test/kotlin/top/yeij/cyrene/data/repository/MessageMergeTest.kt

@@ -0,0 +1,88 @@
+package top.yeij.cyrene.data.repository
+
+import top.yeij.cyrene.data.api.dto.HistoryMessageDto
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class MessageMergeTest {
+
+    private fun msg(id: String, createdAt: Long, content: String = id) = HistoryMessageDto(
+        id = id,
+        sessionId = "web",
+        role = "user",
+        content = content,
+        createdAt = createdAt,
+    )
+
+    private fun idsOf(messages: List<HistoryMessageDto>) = messages.map { it.id }
+
+    @Test
+    fun `overlapping page dedupes by id`() {
+        val existing = listOf(msg("m2", 200), msg("m1", 100))
+        val incoming = listOf(msg("m3", 300), msg("m2", 200))
+
+        val merged = mergeMessages(existing, incoming)
+
+        assertEquals(listOf("m1", "m2", "m3"), idsOf(merged))
+    }
+
+    @Test
+    fun `out of order incoming page is sorted ascending`() {
+        val existing = listOf(msg("m1", 100), msg("m2", 200))
+        val incoming = listOf(msg("m4", 400), msg("m3", 300))
+
+        val merged = mergeMessages(existing, incoming)
+
+        assertEquals(listOf("m1", "m2", "m3", "m4"), idsOf(merged))
+    }
+
+    @Test
+    fun `same millisecond falls back to id ordering`() {
+        val existing = listOf(msg("b", 100), msg("a", 100))
+        val incoming = listOf(msg("c", 100))
+
+        val merged = mergeMessages(existing, incoming)
+
+        assertEquals(listOf("a", "b", "c"), idsOf(merged))
+    }
+
+    @Test
+    fun `empty incoming page keeps existing`() {
+        val existing = listOf(msg("m1", 100), msg("m2", 200))
+
+        val merged = mergeMessages(existing, emptyList())
+
+        assertEquals(listOf("m1", "m2"), idsOf(merged))
+    }
+
+    @Test
+    fun `empty existing returns sorted incoming`() {
+        val incoming = listOf(msg("m3", 300), msg("m1", 100))
+
+        val merged = mergeMessages(emptyList(), incoming)
+
+        assertEquals(listOf("m1", "m3"), idsOf(merged))
+    }
+
+    @Test
+    fun `incoming wins on duplicate id`() {
+        val existing = listOf(msg("m1", 100, content = "old"))
+        val incoming = listOf(msg("m1", 100, content = "new"))
+
+        val merged = mergeMessages(existing, incoming)
+
+        assertEquals(1, merged.size)
+        assertEquals("new", merged.single().content)
+    }
+
+    @Test
+    fun `merge does not mutate inputs`() {
+        val existing = listOf(msg("m2", 200), msg("m1", 100))
+        val incoming = listOf(msg("m3", 300))
+
+        mergeMessages(existing, incoming)
+
+        assertEquals(listOf("m2", "m1"), idsOf(existing))
+        assertEquals(listOf("m3"), idsOf(incoming))
+    }
+}