Compact single-line tool output for file operations and shell

Implement compact display format for read_file, write_file, str_replace, and shell:

- read_file/write_file/str_replace: Single line with dimmed summary and timing
  Format: ● tool_name | path [range] | summary | tokens ◉ time

- shell: Two-line format with command header and dimmed output
  Format: ● shell | command
          └─ output (N lines) | tokens ◉ time

Changes:
- Add print_tool_compact() method to UiWriter trait
- Add is_shell_compact state tracking in ConsoleUiWriter
- Add format_write_file_summary() and format_str_replace_summary() helpers
- Fix duplicate response output by checking if response is empty before printing
- Add finish_streaming_markdown() call before return to flush markdown buffer

crates/g3-cli/src/lib.rs

@@ -220,7 +220,10 @@ async fn run_console_mode(
         let result = agent
             .execute_task_with_timing(&task, None, false, cli.show_prompt, cli.show_code, true, None)
             .await?;
-        output.print_smart(&result.response);
+        // Only print response if it's not empty (streaming already displayed it)
+        if !result.response.trim().is_empty() {
+            output.print_smart(&result.response);
+        }
 
         if let Err(e) = agent.send_auto_memory_reminder().await {
             debug!("Auto-memory reminder failed: {}", e);