Fix tool results visibility, dynamic system prompt, rebrand Galaxy AI to Galaxy

- Rewrite extract_system_prompt to dynamically include CWD, OS, shell, git,
  project rules, and tool usage guidance from request context
- Fix extract_tool_result_content and format_tool_call_result to properly
  handle Grep, FileGlobV2, and ApplyFileDiffs results (were returning empty
  'Tool completed successfully' strings - model never saw file lists)
- Rename all 'Galaxy AI' references to just 'Galaxy' (menu, window title,
  bundle names, plist, welcome text, about)
- Update smoke test with file visibility test prompt
- Suppress dead_code warnings on unused smoke test functions

app/src/pane_group/pane/get_started_view.rs

@@ -229,7 +229,7 @@ impl GetStartedView {
                 .finish(),
                 appearance
                     .ui_builder()
-                    .paragraph("Welcome to Galaxy AI")
+                    .paragraph("Welcome to Galaxy")
                     .with_style(UiComponentStyles {
                         font_size: Some(20.),
                         ..Default::default()