fix(ui): move Save to the first tab stop in the comment popover footer

[balasivagn]

Summary

• Reorders the comment popover footer (packages/ui/components/CommentPopover.tsx) so Save is the first focusable control after the textarea, ahead of Ask AI and the image-upload button.
• Tab order previously matched left-to-right DOM order (image icon → Ask AI → Save), so a fast keyboard flow (select text → comment → Tab, Tab, Enter) could land on the image-upload button instead of Save — the opposite of what you'd want for the primary action.
• Pure reorder: no handler, class, or behavior changes. Mod+Enter/Escape are unaffected (they're wired on the textarea's onKeyDown, independent of button DOM position). Applied identically to both duplicated footer blocks in the file (dialog/expanded mode and popover mode). Since CommentPopover is shared, this fixes both the plan-review and code-review surfaces.

Fixes #1121

Test plan

• packages/ui typechecks clean (tsc --noEmit on packages/ui/tsconfig.json and tsconfig.strict-consumer.json)
• bun test — full suite passes (3 pre-existing, unrelated failures in packages/core/crypto.test.ts hitting the live paste service over the network, not touched by this change)
• Rebuilt apps/review + apps/hook bundles and manually verified in the review-editor dev server: Save appears leftmost, and tabbing from the textarea reaches Save before Ask AI / the image icon, in both the inline popover and expanded dialog variants