fix(proxy): reduce unnecessary Copilot premium interaction consumption

- Fix request classification: treat messages containing tool_result as
  agent continuation instead of user-initiated, preventing false premium
  charges on every tool call
- Add subagent detection via __SUBAGENT_MARKER__ and metadata._agent_
  fallback, setting x-interaction-type=conversation-subagent
- Add deterministic x-interaction-id derived from session ID to group
  requests into a single billing interaction
- Add orphan tool_result sanitization to prevent upstream API errors
  that could cause retries and duplicate billing
- Reorder pipeline: classify (on original body) → sanitize → merge →
  warmup, ensuring classification sees raw tool_result semantics
- Enable warmup downgrade by default with gpt-5-mini model
- Enhance session ID extraction priority chain for Copilot cache keys
- Detect infinite whitespace bug in streaming tool call arguments

src-tauri/src/proxy/providers/claude.rs

@@ -81,13 +81,50 @@ pub fn transform_claude_request_for_api_format(
     provider: &Provider,
     api_format: &str,
 ) -> Result<serde_json::Value, ProxyError> {
-    match api_format {
-        "openai_responses" => {
-            let cache_key = provider
+    // Copilot 场景：优先从 metadata.user_id 提取 session ID 作为 cache key
+    // 格式: "uuid_sessionId" → 提取 "_" 后面的部分作为 session 标识
+    // 同一会话的请求共享 cache key，提升 Copilot 缓存命中率
+    let is_copilot = provider
+        .meta
+        .as_ref()
+        .and_then(|m| m.provider_type.as_deref())
+        == Some("github_copilot")
+        || provider
+            .settings_config
+            .get("baseUrl")
+            .and_then(|v| v.as_str())
+            .is_some_and(|u| u.contains("githubcopilot.com"));
+    let session_cache_key: Option<String> = if is_copilot {
+        let metadata = body.get("metadata");
+        // Session 提取优先级（与 forwarder 和 session.rs 统一）：
+        //   1. metadata.user_id 中的 _session_ 后缀
+        //   2. metadata.session_id（直接字段）
+        metadata
+            .and_then(|m| m.get("user_id"))
+            .and_then(|v| v.as_str())
+            .and_then(super::super::session::parse_session_from_user_id)
+            .or_else(|| {
+                metadata
+                    .and_then(|m| m.get("session_id"))
+                    .and_then(|v| v.as_str())
+                    .filter(|s| !s.is_empty())
+                    .map(|s| s.to_string())
+            })
+    } else {
+        None
+    };
+
+    let cache_key = session_cache_key
+        .as_deref()
+        .or_else(|| {
+            provider
                 .meta
                 .as_ref()
                 .and_then(|m| m.prompt_cache_key.as_deref())
-                .unwrap_or(&provider.id);
+        })
+        .unwrap_or(&provider.id);
+    match api_format {
+        "openai_responses" => {
             // Codex OAuth (ChatGPT Plus/Pro 反代) 需要在请求体里强制 store: false
             // + include: ["reasoning.encrypted_content"]，由 transform 层统一处理。
             let is_codex_oauth = provider
@@ -455,6 +492,7 @@ impl ProviderAdapter for ClaudeAdapter {
                         HeaderName::from_static("x-interaction-type"),
                         HeaderValue::from_static("conversation-agent"),
                     ),
+                    // x-interaction-id 由 forwarder 按需注入（仅在有 session 时）
                     (
                         HeaderName::from_static("x-vscode-user-agent-library-version"),
                         HeaderValue::from_static("electron-fetch"),