Upgrade default Claude Opus model to 4.8

Bump the default Opus route/model from claude-opus-4-7 to claude-opus-4-8
across provider presets (claude, claudeDesktop, hermes, openclaw, opencode,
universal), i18n locales (zh/en/ja/zh-TW), pricing seed data, and the
user-manual docs.

- Add claude-opus-4-8 pricing row ($5/$25/$0.50/$6.25); keep the 4-7 row
  for historical usage stats (seeded via INSERT OR IGNORE).
- Claude Desktop proxy: accept bidirectional opus 4-7 <-> 4-8 route alias
  during rollout so previously saved routes keep resolving.
- thinking_optimizer: route opus-4-8 through adaptive thinking and normalize
  dotted model ids (also fixes dotted 4-6/4-7 falling back to legacy).
- usage_stats: normalize Bedrock/Vertex/aggregator opus-4-8 ids to base
  pricing.

Also merge role:"system" messages into the Gemini systemInstruction in the
Anthropic->Gemini transform.

src-tauri/src/services/usage_stats.rs

@@ -3214,6 +3214,11 @@ mod tests {
             result.is_some(),
             "Claude Desktop 短路由 claude-haiku-4-5 应能匹配到 claude-haiku-4-5-20251001"
         );
+        let result = find_model_pricing_row(&conn, "anthropic/claude-opus-4.8")?;
+        assert!(
+            result.is_some(),
+            "聚合商点号格式 anthropic/claude-opus-4.8 应能匹配到 claude-opus-4-8"
+        );
 
         // Claude Desktop 旧版/异常包装的非 Anthropic route：claude-gpt-5.5 → gpt-5.5
         let result = find_model_pricing_row(&conn, "claude-gpt-5.5")?;
@@ -3229,6 +3234,16 @@ mod tests {
             result.is_some(),
             "Bedrock/Vertex 风格 Claude 模型 ID 应能归一化到基础 Claude 模型定价"
         );
+        let result = find_model_pricing_row(&conn, "global.anthropic.claude-opus-4-8-v1:0")?;
+        assert!(
+            result.is_some(),
+            "Bedrock 风格 Claude Opus 4.8 模型 ID 应能归一化到基础 Claude 模型定价"
+        );
+        let result = find_model_pricing_row(&conn, "claude-opus-4-8@20260527")?;
+        assert!(
+            result.is_some(),
+            "Vertex 风格 Claude Opus 4.8 模型 ID 应能归一化到基础 Claude 模型定价"
+        );
 
         // Reasoning effort 后缀：没有专门价格时回退到基础模型
         let result = find_model_pricing_row(&conn, "gpt-5.4@low")?;