fix(career): passport review polish — a11y semantics + seen-state guard (#937)

CodeRabbit follow-up on #936 (the one Major — overlay outside the click
root — was verified false: the host mounts every screen.html root inside
#plugin-career, ✕-close confirmed working live):

- Tabs: aria-selected/aria-controls + role=tabpanel/aria-labelledby.
- Book overlay: role=dialog + aria-modal + aria-label; focus moves to
  the close button on open and returns to the opener on close.
- seenBadges(): guard non-object JSON so a corrupt stored value cannot
  throw on every passport refresh (covered by a new corruption test).
- Fresh-session suppression test (badge seen → no re-notification).
- Stylelint declaration-empty-line-before nit in .pp-stamp.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

plugins/career/assets/career.css

@@ -257,6 +257,7 @@
 /* The rubber stamp */
 .pp-stamp {
     --pp-rot: 0deg;
+
     position: relative;
     display: flex;
     flex-direction: column;