Closes #644.

What was wrong

Two real gaps in how the changelist bulk-action handler treated a result.redirect envelope from the API runner:

1. No await refresh() on the redirect path. Per Django admin's ModelAdmin.response_action contract, an action that returns a redirect can ALSO have applied side-effects to the rows (reprocess + redirect to status page, regenerate + redirect to download, …). The previous code return-ed before refresh, so those side-effects weren't reflected until the next manual reload.

2. Popup-blocker silently swallowed the redirect. window.open returns null when the call happens past the direct-user-gesture moment (we're inside an async continuation after the POST resolves). The previous code ignored that null, so the operator saw "opened in a new tab" but nothing opened.

Fix

• window.open return value checked. On null, render an amber fallback banner with a clickable link (<a target="_blank" rel="noopener noreferrer">) so the redirect URL is never lost. Dismiss button clears the banner.
• refresh() now fires on BOTH branches.
• Generic " — N item(s)" success toast suppressed on the redirect path — the redirect's destination usually surfaces the next-step UX, so an extra "Done" toast adds noise.

The redirect path itself still uses noopener,noreferrer (reverse-tabnabbing + referer-leak defence) per the issue's stated security stance — those flags were already there.

Refactor for testability

Extracted handleActionResult(...) as a pure helper next to ListPage.tsx so the redirect / popup-blocked / refresh / messages-toast flow is unit-testable without rendering the whole page. window.open and setPendingRedirect are dependency-injected (openLink, onPopupBlocked args) so the test suite can lock the branching without touching jsdom's non-configurable navigation surface.

Dep bump

django-admin-rest-api ^1.1.0 constraint resolved to 1.1.1 in the lock (the README-sync release that documents the security improvements landed in 1.0.7+ — actions runner DoS guard + history field-name redaction + settings hygiene checks).

Verification

• pnpm test — 194 / 194 ✓ (up from 187; +7 new in action-result.test.ts)
• pnpm -r typecheck ✓
• pnpm lint ✓
• pnpm -w build ✓

The seven new tests cover:

1. Redirect → openLink → info toast.
2. Redirect → openLink returns null (popup blocker) → onPopupBlocked called, NO info toast.
3. Refresh fires on both branches.
4. messages[] toasts by level (error → red, info → blue, success → green).
5. No messages + no redirect → generic " — N item(s)" toast.
6. Singular "item" when count is 1.
7. No generic toast on the redirect path (destination surfaces next-step UX).

What's NOT in this PR

• Playwright e2e test (the issue lists this as an acceptance criterion but the project memory steers away from Playwright/Cypress tooling). The vitest covering the same flow via dependency injection meets the issue's "or equivalent" clause.

🤖 Generated with Claude Code