feat(copilot-ui): render reasoning as Markdown, dimmed for human eyes

- Add context::reasoning_to_markdown, outputs Markdown with bold
  headers, fenced KCL, and pretty JSON so the Copilot pane is not a
  wall of text
- UI now renders markdown to lines and dims reasoning text, replaces
  format_reasoning for cleaner output

Signed-off-by: Jessie Frazelle <[email protected]>

Author: jessfraz

src/context.rs

@@ -741,6 +741,90 @@ pub(crate) fn format_reasoning(reason: kittycad::types::ReasoningMessage, use_co
     }
 }
 
+/// Render a ReasoningMessage as Markdown with a bold header and
+/// pretty-printed structured content. Intended for Copilot UI rendering.
+pub(crate) fn reasoning_to_markdown(reason: &kittycad::types::ReasoningMessage) -> String {
+    use serde_json::json;
+
+    match reason {
+        kittycad::types::ReasoningMessage::Text { content } => {
+            format!("**Reasoning**\n\n{}", content.trim())
+        }
+        kittycad::types::ReasoningMessage::KclDocs { content } => {
+            format!("**KCL Docs**\n\n{}", content.trim())
+        }
+        kittycad::types::ReasoningMessage::KclCodeExamples { content } => {
+            format!("**KCL Examples**\n\n{}", content.trim())
+        }
+        kittycad::types::ReasoningMessage::FeatureTreeOutline { content } => {
+            format!("**Feature Tree**\n\n{}", content.trim())
+        }
+        kittycad::types::ReasoningMessage::DesignPlan { steps } => {
+            let mut md = String::from("**Design Plan**\n");
+            for step in steps {
+                let obj = json!({
+                    "file": step.filepath_to_edit,
+                    "edit_instructions": step.edit_instructions,
+                });
+                let pretty = serde_json::to_string_pretty(&obj).unwrap_or_else(|_| obj.to_string());
+                md.push_str("\n```json\n");
+                md.push_str(&pretty);
+                md.push_str("\n```\n");
+            }
+            md
+        }
+        kittycad::types::ReasoningMessage::GeneratedKclCode { code } => {
+            // Keep as fenced code for readability; UI flattens to lines.
+            let mut md = String::from("**Generated KCL**\n\n");
+            md.push_str("```kcl\n");
+            md.push_str(code);
+            md.push_str("\n```\n");
+            md
+        }
+        kittycad::types::ReasoningMessage::KclCodeError { error } => {
+            let mut md = String::from("**KCL Error**\n\n");
+            md.push_str("```text\n");
+            md.push_str(error.trim());
+            md.push_str("\n```\n");
+            md
+        }
+        kittycad::types::ReasoningMessage::CreatedKclFile { file_name, content } => {
+            let meta = json!({ "action": "created", "file": file_name });
+            let mut md = String::from("**Created File**\n\n");
+            md.push_str("```json\n");
+            md.push_str(&serde_json::to_string_pretty(&meta).unwrap_or_else(|_| meta.to_string()));
+            md.push_str("\n```\n");
+            if !content.trim().is_empty() {
+                md.push_str("\n```kcl\n");
+                md.push_str(content);
+                md.push_str("\n```\n");
+            }
+            md
+        }
+        kittycad::types::ReasoningMessage::UpdatedKclFile { file_name, content } => {
+            let meta = json!({ "action": "updated", "file": file_name });
+            let mut md = String::from("**Updated File**\n\n");
+            md.push_str("```json\n");
+            md.push_str(&serde_json::to_string_pretty(&meta).unwrap_or_else(|_| meta.to_string()));
+            md.push_str("\n```\n");
+            if !content.trim().is_empty() {
+                md.push_str("\n```kcl\n");
+                md.push_str(content);
+                md.push_str("\n```\n");
+            }
+            md
+        }
+        kittycad::types::ReasoningMessage::DeletedKclFile { file_name } => {
+            let meta = json!({ "action": "deleted", "file": file_name });
+            let mut md = String::from("**Deleted File**\n\n");
+            md.push_str("```json\n");
+            md.push_str(&serde_json::to_string_pretty(&meta).unwrap_or_else(|_| meta.to_string()));
+            md.push_str("\n```\n");
+            md
+        }
+    }
+}
+
 fn indent_block(s: &str) -> String {
     let mut out = String::new();
     for line in s.lines() {

src/ml/copilot/ui.rs

@@ -117,10 +117,12 @@ pub fn draw(frame: &mut Frame, app: &App) {
                     }
                 }
                 kittycad::types::MlCopilotServerMessage::Reasoning(reason) => {
-                    for l in crate::context::format_reasoning(reason.clone(), false) {
+                    // Render reasoning as dimmed markdown lines for readability.
+                    let md = crate::context::reasoning_to_markdown(reason);
+                    for l in render_markdown_to_lines(&md) {
                         lines.push(Line::from(vec![
                             Span::styled("ML-ephant> ", Style::default().fg(Color::Green)),
-                            Span::raw(l),
+                            Span::styled(l, Style::default().fg(Color::Rgb(150, 150, 150))),
                         ]));
                     }
                 }