Fix compact tool failure display to use single-line format

When compact tools (read_file, write_file, str_replace, etc.) failed,
they would fall through to the non-compact output path, causing:
- Missing or incorrect headers
- Stray footers with wrong formatting
- State leakage (is_shell_compact) between tool calls

Now failed compact tools display in the same single-line format as
successful ones, just with a truncated error message instead of the
success summary:

  ● read_file | path/to/file.txt | ❌ Failed to read file... | 123 ◉ 0ms

This keeps the UI consistent and avoids the "stray footer" bug.

crates/g3-core/src/lib.rs

@@ -2194,7 +2194,12 @@ impl<W: UiWriter> Agent<W> {
                                 let is_todo_tool =
                                     tool_call.tool == "todo_read" || tool_call.tool == "todo_write";
 
-                                if is_compact_tool && tool_success {
+                                if is_compact_tool {
+                                    // For failed compact tools, show truncated error message
+                                    if !tool_success {
+                                        let error_msg = streaming::truncate_for_display(&tool_result, 60);
+                                        Some(error_msg)
+                                    } else {
                                     // Generate appropriate summary based on tool type
                                     match tool_call.tool.as_str() {
                                         "read_file" => Some(streaming::format_read_file_summary(output_len, tool_result.len())),
@@ -2227,6 +2232,7 @@ impl<W: UiWriter> Agent<W> {
                                         }
                                         _ => Some(format!("✅ completed"))
                                     }
+                                    }
                                 } else if is_todo_tool {
                                     // Skip - todo tools print their own content
                                     None