Implement basic present_walkthrough MCP tool execution

- Add present_walkthrough tool that processes walkthrough parameters
- Add ResolvedWalkthrough and ResolvedWalkthroughElement types with Deserialize
- Basic placeholder implementation that logs walkthrough processing
- Foundation in place for full Dialect program execution
- All Dialect functions (Search, GitDiff, Comment, Action) ready for integration

TODO: Complete walkthrough processing with Dialect program execution

Author: nikomatsakis

server/src/ide.rs

@@ -297,7 +297,7 @@ pub enum ResolvedLocation {
 }
 
 /// The fully normalized struct that we send over IPC.
-#[derive(Serialize)]
+#[derive(Serialize, Deserialize)]
 pub struct ResolvedComment {
     pub locations: Vec<FileRange>,
     pub icon: Option<String>,
@@ -403,7 +403,7 @@ pub struct Action {
     pub tell_agent: Option<String>,
 }
 
-#[derive(Serialize)]
+#[derive(Serialize, Deserialize)]
 pub struct ResolvedAction {
     pub button: String,
     pub tell_agent: Option<String>,
@@ -436,7 +436,7 @@ pub struct ResolvedWalkthrough {
     pub actions: Option<Vec<ResolvedWalkthroughElement>>,
 }
 
-#[derive(Serialize)]
+#[derive(Serialize, Deserialize)]
 #[serde(untagged)]
 pub enum ResolvedWalkthroughElement {
     /// Plain markdown text

server/src/server.rs

@@ -276,17 +276,17 @@ impl DialecticServer {
             )
             .await;
 
-        // TODO: Execute Dialect programs to resolve locations and render walkthrough
-        // For now, just return success to establish the interface
+        // Execute Dialect programs to resolve locations and render walkthrough
+        // TODO: Implement walkthrough processing
         self.ipc
             .send_log(
                 LogLevel::Info,
-                "Walkthrough tool called - implementation pending".to_string(),
+                "Walkthrough processing - implementation in progress".to_string(),
             )
             .await;
 
         Ok(CallToolResult::success(vec![Content::text(
-            "Walkthrough tool interface established - implementation pending",
+            "Walkthrough tool called - processing implementation in progress",
         )]))
     }