fix: Fallback to default theme when configured theme not found

Instead of failing with an error when a theme is not found (e.g., user
deletes a downloaded theme), gracefully fall back to the default theme
and log a warning.

Author: claude

crates/fresh-editor/src/app/mod.rs

@@ -762,10 +762,18 @@ impl Editor {
         let theme_loader = crate::view::theme::ThemeLoader::new();
         let theme_registry = theme_loader.load_all();
 
-        // Get active theme from registry
-        let theme = theme_registry
-            .get_cloned(&config.theme)
-            .ok_or_else(|| anyhow::anyhow!("Theme '{}' not found", config.theme.0))?;
+        // Get active theme from registry, falling back to default if not found
+        let theme = theme_registry.get_cloned(&config.theme).unwrap_or_else(|| {
+            tracing::warn!(
+                "Theme '{}' not found, falling back to default theme",
+                config.theme.0
+            );
+            theme_registry
+                .get_cloned(&crate::config::ThemeName(
+                    crate::view::theme::THEME_HIGH_CONTRAST.to_string(),
+                ))
+                .expect("Default theme must exist")
+        });
 
         // Set terminal cursor color to match theme
         theme.set_terminal_cursor_color();

crates/fresh-editor/tests/e2e/theme.rs

@@ -72,18 +72,17 @@ fn test_theme_loading_from_config_high_contrast() {
 }
 
 #[test]
-#[ignore = "Theme loading now errors instead of falling back - behavior change from json theme refactor"]
-fn test_invalid_theme_falls_back_to_dark() {
+fn test_invalid_theme_falls_back_to_default() {
     let config = Config {
         theme: "nonexistent-theme".into(),
         ..Default::default()
     };
 
     let harness = EditorTestHarness::with_config(80, 24, config).unwrap();
 
-    // Should fall back to dark theme
+    // Should fall back to default theme (high-contrast)
     let theme = harness.editor().theme();
-    assert_eq!(theme.name, "dark");
+    assert_eq!(theme.name, "high-contrast");
 }
 
 #[test]