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/app/src/components/status-popover.tsx

@@ -196,7 +196,7 @@ export function StatusPopover() {
       triggerProps={{
         variant: "ghost",
         class:
-          "rounded-md h-[24px] pr-2 pl-0.5 gap-2 border border-border-weak-base bg-surface-panel shadow-none data-[expanded]:bg-surface-raised-base-hover",
+          "rounded-md h-[24px] pr-3 pl-0.5 gap-2 border border-border-weak-base bg-surface-panel shadow-none data-[expanded]:bg-surface-raised-base-hover",
         style: { scale: 1 },
       }}
       trigger={