feat(viewas): convert ViewAsBar to React component using useHotkeys

[sentry-junior]

Summary

Converts the superuser "View As" toolbar from a vanilla JS implementation to a proper React component using useHotkeys from @sentry/scraps/hotkey.

This is the sentry-side change. A companion change in getsentry/getsentry updates getsentry/templates/viewas/header.html to use the __onSentryInit injection pattern instead of inline vanilla JS.

Changes

static/app/components/viewAsBar/index.tsx (new)

• New ViewAsBar React component
• Uses useHotkeys with cmd+`` / ctrl+`` (changed from bare ``` to avoid collision with code block shortcuts)
• Input/textarea focus suppression comes for free via useHotkeys defaults — fixes the Seer code-block triple-backtick collision
• Renders the same toolbar UI (username, switch user form) that the old Django template did
• Passes csrfToken as a prop for the Django form submission

static/app/types/system.tsx

• Added VIEW_AS_BAR = 'ViewAsBar' to SentryInitRenderReactComponent enum

static/app/bootstrap/processInitQueue.tsx

• Registered ViewAsBar in COMPONENT_MAP with lazy import

getsentry changes (apply separately)

The companion getsentry/getsentry diff strips the old HTML/CSS/JS from getsentry/templates/viewas/header.html and replaces it with:

<div id="viewas-bar-root"></div>
<script>
  window.__onSentryInit = window.__onSentryInit || [];
  window.__onSentryInit.push({
    name: 'renderReact',
    component: 'ViewAsBar',
    container: '#viewas-bar-root',
    props: { currentUsername, actualUsername, csrfToken },
  });
</script>

Testing

• Toggle toolbar with `cmd+`` — should open/close
• Try pressing ``` inside any text input or Seer — toolbar should NOT trigger
• Switch user via form and verify Django session handling works as before

Fixes: https://github.com/getsentry/sentry/issues (backtick hotkey collides with Seer code blocks)