feat: Agnes上下文512K→1M + Ollama支持配置num_ctx

Agnes AI:
- adapter注释和API文档更新: 上下文512K→1M (官方已升级)

Ollama num_ctx 支持:
- MetonaGenerationParams 新增 contextLength 字段
- OllamaAdapter.toNativeRequest 发送 options.num_ctx
- AgentLoopEngine 从 config 读取并传递到请求参数
- database.service 新增 ollama.numCtx 默认配置(null=由模型决定)
- SettingsModal LLM设置: Ollama 选中时显示上下文长度输入框
- main.ts 启动时从 configService 读取 ollama.numCtx

数据流:
Settings → configService → main.ts → AgentLoopEngine.config
→ MetonaRequest.params → OllamaAdapter → options.num_ctx

apis/agnes-ai-api-docs-20260625.html

@@ -495,7 +495,7 @@
         <p style="margin-top: 12px;">在 Claw-Eval 基准测试中排名 General Leaderboard <strong style="color:var(--accent)">第 9</strong>，Pass³ 分数 <strong style="color:var(--green)">60.9%</strong>。</p>
         <div class="hero-meta">
             <span><span class="dot dot-blue"></span> 模型名称: <strong>agnes-2.0-flash</strong></span>
-            <span><span class="dot dot-green"></span> 上下文: <strong>512K</strong> | 最大输出: <strong>65.5K</strong></span>
+            <span><span class="dot dot-green"></span> 上下文: <strong>1M</strong> | 最大输出: <strong>65.5K</strong></span>
             <span><span class="dot dot-orange"></span> Base URL: <strong>https://apihub.agnes-ai.com/v1</strong></span>
         </div>
     </div>
@@ -1004,7 +1004,7 @@ response = client.chat.completions.<span class="hl-fn">create</span>(
             <table class="params">
                 <thead><tr><th>项目</th><th>数值</th></tr></thead>
                 <tbody>
-                    <tr><td class="param-name">Context</td><td class="param-type">512K</td></tr>
+                    <tr><td class="param-name">Context</td><td class="param-type">1M</td></tr>
                     <tr><td class="param-name">Max Output</td><td class="param-type">65.5K</td></tr>
                 </tbody>
             </table>