main: 增强会话功能，支持消息管理和接口文档

- 添加 `last_message_id` 字段至 `chat_sessions` 表，更新其关联索引
- 实现会话更新接口，支持修改名称与状态并添加验证逻辑
- 增加会话列表接口，支持状态过滤与关键字查询
- 提供会话和消息相关的资源类和请求验证类
- 扩展 `ChatService` 服务层逻辑以处理会话更新和消息附加
- 编写测试用例以验证新功能的正确性
- 增加接口文档及 OpenAPI 规范文件，覆盖新增功能
- 更新数据库播种器，添加默认用户

tests/Feature/ChatSessionTest.php

@@ -5,6 +5,7 @@ namespace Tests\Feature;
 use App\Enums\ChatSessionStatus;
 use App\Models\User;
 use App\Services\ChatService;
+use Illuminate\Support\Carbon;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use PHPOpenSourceSaver\JWTAuth\Facades\JWTAuth;
 use Tests\TestCase;
@@ -89,7 +90,7 @@ class ChatSessionTest extends TestCase
             'session_name' => 'API Session',
         ])->assertCreated();
 
-        $sessionId = $createSession->json('session_id');
+        $sessionId = $createSession->json('data.session_id');
 
         $append = $this->withHeaders($headers)->postJson("/api/sessions/{$sessionId}/messages", [
             'role' => 'USER',
@@ -105,4 +106,116 @@ class ChatSessionTest extends TestCase
         $this->assertEquals(1, $list->json('data.0.seq'));
         $this->assertEquals('hello api', $list->json('data.0.content'));
     }
+
+    public function test_session_list_sorted_and_last_message_preview(): void
+    {
+        $user = User::factory()->create();
+        $headers = $this->authHeader($user);
+        $service = app(ChatService::class);
+
+        Carbon::setTestNow('2025-01-01 00:00:00');
+        $s1 = $service->createSession('First');
+        $service->appendMessage([
+            'session_id' => $s1->session_id,
+            'role' => 'USER',
+            'type' => 'user.prompt',
+            'content' => 'hello first',
+        ]);
+
+        Carbon::setTestNow('2025-01-01 00:00:10');
+        $s2 = $service->createSession('Second');
+        $service->appendMessage([
+            'session_id' => $s2->session_id,
+            'role' => 'USER',
+            'type' => 'user.prompt',
+            'content' => 'hello second',
+        ]);
+
+        Carbon::setTestNow();
+
+        $resp = $this->withHeaders($headers)->getJson('/api/sessions?per_page=10')
+            ->assertOk();
+
+        $this->assertEquals($s2->session_id, $resp->json('data.0.session_id'));
+        $this->assertEquals('hello second', $resp->json('data.0.last_message_preview'));
+        $this->assertEquals('hello first', $resp->json('data.1.last_message_preview'));
+        $this->assertNotNull($resp->json('data.0.last_message_at'));
+    }
+
+    public function test_session_list_filters_status_and_query(): void
+    {
+        $user = User::factory()->create();
+        $headers = $this->authHeader($user);
+        $service = app(ChatService::class);
+
+        $open = $service->createSession('Alpha');
+        $locked = $service->createSession('Beta');
+        $locked->update(['status' => ChatSessionStatus::LOCKED]);
+        $closed = $service->createSession('Gamma');
+        $closed->update(['status' => ChatSessionStatus::CLOSED]);
+
+        $respStatus = $this->withHeaders($headers)->getJson('/api/sessions?status=LOCKED')
+            ->assertOk();
+        $this->assertCount(1, $respStatus->json('data'));
+        $this->assertEquals($locked->session_id, $respStatus->json('data.0.session_id'));
+
+        $respQuery = $this->withHeaders($headers)->getJson('/api/sessions?q=Alpha')
+            ->assertOk();
+        $this->assertCount(1, $respQuery->json('data'));
+        $this->assertEquals($open->session_id, $respQuery->json('data.0.session_id'));
+    }
+
+    public function test_patch_updates_session_name(): void
+    {
+        $user = User::factory()->create();
+        $headers = $this->authHeader($user);
+        $service = app(ChatService::class);
+        $session = $service->createSession('Old Name');
+
+        $resp = $this->withHeaders($headers)->patchJson("/api/sessions/{$session->session_id}", [
+            'session_name' => 'New Name',
+        ])->assertOk();
+
+        $this->assertEquals('New Name', $resp->json('data.session_name'));
+    }
+
+    public function test_patch_updates_status_transitions(): void
+    {
+        $user = User::factory()->create();
+        $headers = $this->authHeader($user);
+        $service = app(ChatService::class);
+        $session = $service->createSession('Status Session');
+
+        $this->withHeaders($headers)->patchJson("/api/sessions/{$session->session_id}", [
+            'status' => ChatSessionStatus::LOCKED,
+        ])->assertOk()->assertJsonFragment(['status' => ChatSessionStatus::LOCKED]);
+
+        $this->withHeaders($headers)->patchJson("/api/sessions/{$session->session_id}", [
+            'status' => ChatSessionStatus::OPEN,
+        ])->assertOk()->assertJsonFragment(['status' => ChatSessionStatus::OPEN]);
+    }
+
+    public function test_closed_session_cannot_reopen(): void
+    {
+        $user = User::factory()->create();
+        $headers = $this->authHeader($user);
+        $service = app(ChatService::class);
+        $session = $service->createSession('Closed Session');
+        $session->update(['status' => ChatSessionStatus::CLOSED]);
+
+        $this->withHeaders($headers)->patchJson("/api/sessions/{$session->session_id}", [
+            'status' => ChatSessionStatus::OPEN,
+        ])->assertStatus(403);
+    }
+
+    public function test_empty_patch_rejected(): void
+    {
+        $user = User::factory()->create();
+        $headers = $this->authHeader($user);
+        $service = app(ChatService::class);
+        $session = $service->createSession('Patch Empty');
+
+        $this->withHeaders($headers)->patchJson("/api/sessions/{$session->session_id}", [])
+            ->assertStatus(422);
+    }
 }