Show human-readable descriptions in /resume session list

- Add description field to SessionContinuation struct
- Extract first user message (truncated to ~60 chars at word boundary)
- Display as quoted text instead of session ID hash
- Fall back to session ID if no description available

Example: [2 hours ago] 'when I call /resume it only shows me 2 sessions...'

crates/g3-core/src/lib.rs

@@ -1405,10 +1405,20 @@ impl<W: UiWriter> Agent<W> {
             .map(|p| p.to_string_lossy().to_string())
             .unwrap_or_else(|_| ".".to_string());
         
+        // Get description from first user message (strip "Task: " prefix if present)
+        let description = self.context_window.conversation_history.iter()
+            .find(|m| matches!(m.role, g3_providers::MessageRole::User))
+            .map(|m| {
+                let content = m.content.strip_prefix("Task: ").unwrap_or(&m.content);
+                // Truncate to ~60 chars for display, ending at word boundary
+                truncate_to_word_boundary(content, 60)
+            });
+        
         let continuation = SessionContinuation::new(
             self.is_agent_mode,
             self.agent_name.clone(),
             session_id,
+            description,
             summary,
             session_log_path.to_string_lossy().to_string(),
             self.context_window.percentage_used(),
@@ -2831,6 +2841,24 @@ impl<W: UiWriter> Agent<W> {
 // Re-export utility functions
 pub use utils::apply_unified_diff_to_string;
 
+/// Truncate a string to approximately max_len characters, ending at a word boundary
+fn truncate_to_word_boundary(s: &str, max_len: usize) -> String {
+    if s.len() <= max_len {
+        return s.to_string();
+    }
+    
+    // Find the last space before max_len
+    let truncated = &s[..max_len];
+    if let Some(last_space) = truncated.rfind(' ') {
+        if last_space > max_len / 2 {
+            // Only use word boundary if it's not too short
+            return format!("{}...", &s[..last_space]);
+        }
+    }
+    // Fall back to character truncation
+    format!("{}...", truncated)
+}
+
 // Implement Drop to clean up safaridriver process
 impl<W: UiWriter> Drop for Agent<W> {
     fn drop(&mut self) {

crates/g3-core/src/session_continuation.rs

@@ -32,6 +32,9 @@ pub struct SessionContinuation {
     pub created_at: String,
     /// Original session ID
     pub session_id: String,
+    /// Human-readable description (first user message, truncated)
+    #[serde(default)]
+    pub description: Option<String>,
     /// Session summary (last assistant response)
     pub summary: Option<String>,
     /// Path to the full session log (g3_session_*.json)
@@ -50,6 +53,7 @@ impl SessionContinuation {
         is_agent_mode: bool,
         agent_name: Option<String>,
         session_id: String,
+        description: Option<String>,
         summary: Option<String>,
         session_log_path: String,
         context_percentage: f32,
@@ -62,6 +66,7 @@ impl SessionContinuation {
             agent_name,
             created_at: chrono::Utc::now().to_rfc3339(),
             session_id,
+            description,
             summary,
             session_log_path,
             context_percentage,