Story Share portal: Safety Exit quick-escape button

Context

The Story Share portal (/story_shares) serves an audience that includes domestic-violence survivors. The live WordPress site (stories.awbw.org) has a prominent "Safety Exit" button that lets a visitor leave the site instantly.

An initial JS implementation (a safety_exit Stimulus controller doing window.open + location.replace) was built and then removed from the portal-parity PR (#2148) to keep it lean — and because a plain no-JS link gives false security (it navigates away but doesn't scrub browser history, so the back button still returns to the story).

What's needed

• A Safety Exit control that meaningfully protects the visitor:
  • Navigates away to a neutral site (e.g. weather.com) immediately.
  • Scrubs/replaces history so the back button doesn't return to the portal (location.replace, and ideally overwrite prior entries).
  • Optionally opens a decoy tab and/or clears the current tab's content first.
  • Keyboard shortcut (the WP site / common patterns use a quick key) and a fixed, always-visible button on every portal page, including mobile.
• Accessibility: clearly labeled, high-contrast, reachable without scrolling.
• Document the inherent limitation (client-side JS cannot fully erase browser history) and decide whether that's acceptable or whether to add guidance.

Notes

Prior implementation for reference is in the git history of PR #2148 (app/frontend/javascript/controllers/safety_exit_controller.js, since removed).

Review the removed app/frontend/javascript/controllers/safety_exit_controller.js and the portal-parity changes in PR #2148 first. Trace how the /story_shares portal renders across pages and mobile, then define and verify an accessible, always-visible control and keyboard shortcut whose navigation and history behavior match the agreed safety requirements; document the client-side history limitation.