feat(providers): implement chat_with_history for GLM provider

The GLM provider previously relied on the trait default for
chat_with_history, which only forwarded the last user message. This adds
a proper multi-turn implementation that sends the full conversation
history to the GLM API, matching the pattern used by OpenRouter, Ollama,
and other providers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/providers/glm.rs

@@ -2,7 +2,7 @@
 //! The GLM API requires JWT tokens generated from the `id.secret` API key format
 //! with a custom `sign_type: "SIGN"` header, and uses `/v4/chat/completions`.
 
-use crate::providers::traits::Provider;
+use crate::providers::traits::{ChatMessage, Provider};
 use async_trait::async_trait;
 use reqwest::Client;
 use ring::hmac;
@@ -206,6 +206,53 @@ impl Provider for GlmProvider {
             .map(|c| c.message.content)
             .ok_or_else(|| anyhow::anyhow!("No response from GLM"))
     }
+
+    async fn chat_with_history(
+        &self,
+        messages: &[ChatMessage],
+        model: &str,
+        temperature: f64,
+    ) -> anyhow::Result<String> {
+        let token = self.generate_token()?;
+
+        let api_messages: Vec<Message> = messages
+            .iter()
+            .map(|m| Message {
+                role: m.role.clone(),
+                content: m.content.clone(),
+            })
+            .collect();
+
+        let request = ChatRequest {
+            model: model.to_string(),
+            messages: api_messages,
+            temperature,
+        };
+
+        let url = format!("{}/chat/completions", self.base_url);
+
+        let response = self
+            .client
+            .post(&url)
+            .header("Authorization", format!("Bearer {token}"))
+            .json(&request)
+            .send()
+            .await?;
+
+        if !response.status().is_success() {
+            let error = response.text().await?;
+            anyhow::bail!("GLM API error: {error}");
+        }
+
+        let chat_response: ChatResponse = response.json().await?;
+
+        chat_response
+            .choices
+            .into_iter()
+            .next()
+            .map(|c| c.message.content)
+            .ok_or_else(|| anyhow::anyhow!("No response from GLM"))
+    }
 }
 
 #[cfg(test)]
@@ -268,6 +315,19 @@ mod tests {
         assert!(result.is_err());
     }
 
+    #[tokio::test]
+    async fn chat_with_history_fails_without_key() {
+        let p = GlmProvider::new(None);
+        let messages = vec![
+            ChatMessage::system("You are helpful."),
+            ChatMessage::user("Hello"),
+            ChatMessage::assistant("Hi there!"),
+            ChatMessage::user("What did I say?"),
+        ];
+        let result = p.chat_with_history(&messages, "glm-4.7", 0.7).await;
+        assert!(result.is_err());
+    }
+
     #[test]
     fn base64url_no_padding() {
         let encoded = base64url_encode_bytes(b"hello");