• Shortened the Contrast button label across all six locales so it
  doesn't overflow on narrow displays.
• Visual identity polish to align with ace.useit.se: 8px rounded
  corners, Aceit petrol on the active mode button, brand font stack
  (Roboto Flex / Poppins with system fallbacks).

No new permissions, no functional changes.

Accessibility improvements for screen-reader users:
- Theme toggle now announces both the action ("Switch to light theme")
and the current state ("currently shown with a dark theme").
- Selected mode now announces "[Mode name]. Selected." instead of
having the visual checkmark glyph read aloud.
- The popup stays open after activating a mode so the live region
announces the element/warning count. Sighted users can dismiss it
by clicking outside or pressing Escape.

Visual:
- Sun icon in dark mode now uses Aceit's "sunny" yellow.

Localisation:
- Swedish store description rewritten in more natural Swedish; lowercased
technology acronyms per Swedish typography conventions.
- Norwegian store description corrected by a native reviewer
("universell utforming").
- Updated mode tooltips for clarity (Headings, Tables, Text, Links &
buttons, Disable CSS, Lists, Forms).
- Added tooltip for the Contrast checker shortcut.

Code quality / cleanup:
- Removed unused popup_themeToggle locale key.

No new permissions, no new code paths beyond the locale layer.
The package still uses only activeTab and scripting permissions,
no telemetry, no storage permission.

• Updated Swedish store description copy for natural Swedish phrasing
  ("Verktyg för att testa tillgängligheten i webbgränssnitt").
• Lowercased acronyms in Swedish text per Swedish typography conventions.

No code changes, no permission changes — text-only update.