tui: improve modified file visibility and button spacing

- Replace warning yellow with distinct orange color for modified files in git diff indicators
- Increase button padding for better visual balance in session header and status popover

packages/ui/src/styles/theme.css

@@ -287,7 +287,7 @@
   --icon-diff-add-active: var(--mint-light-12);
   --icon-diff-delete-base: var(--ember-light-10);
   --icon-diff-delete-hover: var(--ember-light-11);
-  --icon-diff-modified-base: var(--icon-warning-base);
+  --icon-diff-modified-base: #ff8c00;
   --syntax-comment: var(--text-weak);
   --syntax-regexp: var(--text-base);
   --syntax-string: #006656;
@@ -545,7 +545,7 @@
     --icon-diff-add-active: var(--mint-dark-11);
     --icon-diff-delete-base: var(--ember-dark-9);
     --icon-diff-delete-hover: var(--ember-dark-10);
-    --icon-diff-modified-base: var(--icon-warning-base);
+    --icon-diff-modified-base: #ffba92;
     --syntax-comment: var(--text-weak);
     --syntax-regexp: var(--text-base);
     --syntax-string: #00ceb9;

packages/ui/src/theme/resolve.ts

@@ -240,7 +240,7 @@ export function resolveThemeVariant(variant: ThemeVariant, isDark: boolean): Res
   tokens["icon-diff-add-active"] = diffAdd[isDark ? 10 : 11]
   tokens["icon-diff-delete-base"] = diffDelete[isDark ? 8 : 9]
   tokens["icon-diff-delete-hover"] = diffDelete[isDark ? 9 : 10]
-  tokens["icon-diff-modified-base"] = tokens["icon-warning-base"]
+  tokens["icon-diff-modified-base"] = isDark ? "#ffba92" : "#FF8C00"
 
   tokens["syntax-comment"] = "var(--text-weak)"
   tokens["syntax-regexp"] = "var(--text-base)"