fix(copilot): resolve Claude model IDs against live /models list

Copilot upstream returns model_not_supported when the client sends
dash-form Claude IDs (claude-sonnet-4-6, claude-sonnet-4-6[1m]) while
/models only accepts dot form (claude-sonnet-4.6, -1m suffix).

- Add copilot_model_map: syntax normalize (dash->dot, [1m]->-1m) plus
  live /models exact match and family-version fallback, reusing the
  existing 5 min auth cache. Returns None when the whole family is
  absent so upstream surfaces an explicit error instead of silently
  switching families.
- Wire into forwarder Copilot hook; runs before anthropic_to_openai
  conversion.
- Default Opus slot in the Copilot preset maps to Sonnet 4.6: Pro
  dropped all Opus on 2026-04-20 and Pro+ bills Opus 4.7 at 7.5x.
  Users who want real Opus can switch manually in the UI.

Refs: https://github.com/farion1231/cc-switch/issues/2016

src-tauri/src/proxy/forwarder.rs

@@ -790,6 +790,13 @@ impl RequestForwarder {
             == Some("github_copilot")
             || base_url.contains("githubcopilot.com");
 
+        if is_copilot {
+            mapped_body =
+                super::providers::copilot_model_map::apply_copilot_model_normalization(mapped_body);
+            self.apply_copilot_live_model_resolution(provider, &mut mapped_body)
+                .await;
+        }
+
         // --- Copilot 优化器：分类 + 请求体优化（在格式转换之前执行） ---
         // 注意：确定性 ID 也在此处计算，因为 mapped_body 在格式转换时会被 move
         //
@@ -1485,6 +1492,49 @@ impl RequestForwarder {
         "openai_chat".to_string()
     }
 
+    /// 用 Copilot live `/models` 列表确认 model ID 真实可用，找不到时按 family 降级。
+    /// 命中缓存后是同步的；首次请求或 5 min 缓存过期后会触发一次 HTTP。
+    async fn apply_copilot_live_model_resolution(
+        &self,
+        provider: &Provider,
+        body: &mut serde_json::Value,
+    ) {
+        let Some(model_id) = body.get("model").and_then(|v| v.as_str()) else {
+            return;
+        };
+        let model_id = model_id.to_string();
+
+        let Some(app_handle) = &self.app_handle else {
+            return;
+        };
+        let copilot_state = app_handle.state::<CopilotAuthState>();
+        let copilot_auth = copilot_state.0.read().await;
+        let account_id = provider
+            .meta
+            .as_ref()
+            .and_then(|m| m.managed_account_id_for("github_copilot"));
+
+        let models_result = match account_id.as_deref() {
+            Some(id) => copilot_auth.fetch_models_for_account(id).await,
+            None => copilot_auth.fetch_models().await,
+        };
+
+        let models = match models_result {
+            Ok(m) => m,
+            Err(err) => {
+                log::debug!("[Copilot] live model list unavailable, skip resolution: {err}");
+                return;
+            }
+        };
+
+        if let Some(resolved) =
+            super::providers::copilot_model_map::resolve_against_models(&model_id, &models)
+        {
+            log::info!("[Copilot] live-model resolve: {model_id} → {resolved}");
+            body["model"] = serde_json::Value::String(resolved);
+        }
+    }
+
     async fn is_copilot_openai_vendor_model(&self, provider: &Provider, model_id: &str) -> bool {
         let Some(app_handle) = &self.app_handle else {
             log::debug!("[Copilot] AppHandle unavailable, fallback to chat/completions");