fix: support response parts with extra fields like thoughtSignature

Implement custom Deserialize for Part to tolerate additional response fields (such as thoughtSignature or thought) returned by thinking models.

src/types/common.rs

@@ -83,7 +83,7 @@ impl FromStr for Role {
     }
 }
 
-#[derive(Clone, Debug, Serialize, Deserialize)]
+#[derive(Clone, Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub enum Part {
     Text(String),
@@ -100,3 +100,66 @@ pub enum Part {
         args: HashMap<String, String>,
     },
 }
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct PartHelper {
+    text: Option<String>,
+    inline_data: Option<InlineDataHelper>,
+    file_data: Option<FileDataHelper>,
+    function_call: Option<FunctionCallHelper>,
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct InlineDataHelper {
+    mime_type: String,
+    data: String,
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct FileDataHelper {
+    mime_type: String,
+    file_uri: String,
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct FunctionCallHelper {
+    name: String,
+    args: HashMap<String, String>,
+}
+
+impl<'de> Deserialize<'de> for Part {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let helper = PartHelper::deserialize(deserializer)?;
+        if let Some(text) = helper.text {
+            return Ok(Part::Text(text));
+        }
+        if let Some(inline_data) = helper.inline_data {
+            return Ok(Part::InlineData {
+                mime_type: inline_data.mime_type,
+                data: inline_data.data,
+            });
+        }
+        if let Some(file_data) = helper.file_data {
+            return Ok(Part::FileData {
+                mime_type: file_data.mime_type,
+                file_uri: file_data.file_uri,
+            });
+        }
+        if let Some(function_call) = helper.function_call {
+            return Ok(Part::FunctionCall {
+                name: function_call.name,
+                args: function_call.args,
+            });
+        }
+        Err(serde::de::Error::custom(
+            "Part does not contain any recognizable variant",
+        ))
+    }
+}