feat(runtime): 为上下文超限错误添加自动重试机制

添加 RuntimeError::is_retryable_context_error 方法，用于识别可重试的上下文错误（如令牌超限、上下文窗口超限等）。当对话执行遇到此类错误时，自动触发会话压缩并重试，而非直接失败，提高系统的鲁棒性。

rust/crates/runtime/src/conversation.rs

@@ -95,6 +95,22 @@ impl RuntimeError {
             message: message.into(),
         }
     }
+
+    /// Checks if this error is eligible for automatic retry and self-healing (e.g., via session compaction).
+    /// This list can be expanded in the future as new retryable error types are identified.
+    #[must_use]
+    pub fn is_retryable_context_error(&self) -> bool {
+        let msg = self.message.to_lowercase();
+        let retryable_markers = [
+            // Context window limits that can be fixed by compaction
+            "maximum context length",
+            "too many tokens",
+            "context_length_exceeded",
+            "prompt is too long",
+            "context window",
+        ];
+        retryable_markers.iter().any(|marker| msg.contains(marker))
+    }
 }
 
 impl Display for RuntimeError {
@@ -358,6 +374,7 @@ where
                 Err(error) => {
                     self.record_turn_failed(iterations, &error);
 
+                    if error.is_retryable_context_error() {
                         let result = compact_session(
                             &self.session,
                             CompactionConfig {
@@ -377,6 +394,9 @@ where
                         }
                         continue;
                     }
+
+                    return Err(error);
+                }
             };
             let (assistant_message, usage, turn_prompt_cache_events) =
                 match build_assistant_message(events) {