fix(live): enable node filtering after its handlers are ready

[n30nex]

Red commit: 8974616 (CI assertion failures).

Fixes #2094.

The Live node-filter input now starts natively disabled and becomes editable after its input, keyboard and blur handlers attach. Previously it accepted text while initial node loading was pending, then never processed that text without another keystroke.

The change adds one HTML attribute and one initialization assignment. Failed initial loading still reaches the existing error handler and installs the controls. Saved filters, URL precedence, autocomplete and keyboard selection keep their existing behavior. No new settings, styling, dependencies, requests or packet-processing work.

Validation

• The existing CI-wired Live browser suite delays or aborts the real initial node request. It verifies rejected premature typing, later editability, actual suggestions, keyboard selection and URL state. Both new cases failed on the red commit; all six cases pass locally on 11fab46.
• All 183 standalone frontend suites passed, plus lint and XSS gates. Separate browser checks passed saved-filter restoration and URL override; desktop/mobile loading/ready screenshots were inspected.
• A broader local core run exposed the unchanged stale observation-handle test tracked in test(packets): observation hex test clicks stale DOM handles #2104. It is outside this Live fix. Full CI passed at 11fab46, including Go, browsers and both container architectures; three independent reviews are clear.

E2E assertion added: tests/e2e/test-1110-live-filter.js:69.

Preflight overrides: external script/OpenClaw profile unavailable; repository checks and local Chromium used.