[router] add tool parser base structure and partial json parser (#9482)

sgl-router/src/tool_parser/errors.rs

@@ -0,0 +1,32 @@
+use thiserror::Error;
+
+/// Result type for tool parser operations
+pub type ToolParserResult<T> = Result<T, ToolParserError>;
+
+/// Errors that can occur during tool parsing
+#[derive(Debug, Error)]
+pub enum ToolParserError {
+    #[error("Parsing failed: {0}")]
+    ParsingFailed(String),
+
+    #[error("Model not supported: {0}")]
+    ModelNotSupported(String),
+
+    #[error("Parse depth exceeded: max {0}")]
+    DepthExceeded(usize),
+
+    #[error("Invalid JSON: {0}")]
+    JsonError(#[from] serde_json::Error),
+
+    #[error("Regex error: {0}")]
+    RegexError(#[from] regex::Error),
+
+    #[error("Incomplete tool call")]
+    Incomplete,
+
+    #[error("Invalid tool name: {0}")]
+    InvalidToolName(String),
+
+    #[error("Token not found: {0}")]
+    TokenNotFound(String),
+}