enrich: explicitly filter for text blocks in transcript extraction

Only extract content blocks with "type": "text". Previously relied on
tool_use/tool_result blocks lacking a "text" field, which worked but
was fragile. Now explicitly checks block type.

src/enrich.rs

@@ -97,8 +97,10 @@ fn extract_conversation(jsonl_path: &str) -> Result<Vec<(usize, String, String,
             Some(serde_json::Value::Array(arr)) => {
                 arr.iter()
                     .filter_map(|c| {
-                        if let Some(t) = c.get("text").and_then(|v| v.as_str()) {
+                        // Only extract text blocks; skip tool_use, tool_result, thinking, etc.
-                            Some(t.to_string())
+                        let is_text = c.get("type").and_then(|v| v.as_str()) == Some("text");
+                        if is_text {
+                            c.get("text").and_then(|v| v.as_str()).map(|s| s.to_string())
                         } else {
                             c.as_str().map(|s| s.to_string())
                         }