[mudler-agent]

Description

Stabilize two backend UI tests without changing production behavior:

• Wait for the node-specific, enabled reinstall control before invoking its handler in both deletion-concurrency cases. The generic control shares its accessible name and can remain rendered after a URL update. Assert the exact targeted POST and retain all deletion-conflict checks.
• Seed installed backend inventory for legacy navigation. Assert the rendered selection and complete canonical URL after inventory loads. Cover missing-selection cleanup separately, preserving URL refinements and existing final-node deletion coverage.

These address intermittent assertions in tests introduced by #12785 and #12526. No production code, configuration, timeouts, retries, or coverage gates change.

Notes for Reviewers

Verification uses Chromium, one worker, and retries disabled:

cd core/http/react-ui
npx playwright test e2e/backends-installed-node-removal.spec.js e2e/canonical-resource-navigation.spec.js --retries=0 --workers=1
npx playwright test e2e/backends-installed-node-removal.spec.js --grep 'generic deletion blocks targeted install' --repeat-each=5 --retries=0 --workers=1
npx eslint e2e/backends-installed-node-removal.spec.js e2e/canonical-resource-navigation.spec.js

Before the final exact-request assertion, both complete specs passed (41 tests), and five affected cases passed ten repetitions (50 tests). Independent verification also passed both complete specs. After that assertion, both concurrency variants passed ten local repetitions and six independent repetitions. Targeted lint and diff checks pass.

The original signatures reproduced with retries off. Negative controls confirm that settled navigation rejects absent inventory and cleanup distinguishes present from missing selections. No full-suite or coverage-gate result is claimed.

Signed commits

• Yes, I signed my commits (maintainer DCO sign-off).
• Documentation updated (docs/content/) for user-facing changes, or not applicable — test-only changes.