feat: add deepseek provider scaffolding

src/llm/provider.rs

@@ -0,0 +1,45 @@
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use thiserror::Error;
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct ChatMessage {
+    pub role: String,
+    pub content: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct ToolDefinition {
+    pub name: String,
+    pub description: String,
+    pub parameters: Value,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct ToolFunctionCall {
+    pub id: String,
+    pub name: String,
+    pub arguments: Value,
+}
+
+pub trait LlmProvider {
+    fn chat(
+        &self,
+        messages: &[ChatMessage],
+        tools: &[ToolDefinition],
+    ) -> Result<Vec<ToolFunctionCall>, LlmError>;
+}
+
+#[derive(Debug, Error)]
+pub enum LlmError {
+    #[error(transparent)]
+    Config(#[from] crate::config::ConfigError),
+    #[error(transparent)]
+    Http(#[from] reqwest::Error),
+    #[error(transparent)]
+    Json(#[from] serde_json::Error),
+    #[error("llm returned no tool calls")]
+    NoToolCalls,
+    #[error("llm returned malformed tool arguments: {0}")]
+    InvalidToolArguments(String),
+}