[feritcemkahraman]

Moving a <task-lists> element out of and back into the document adds another change listener each time. After two reconnections, one checkbox change emits three task-lists-check events, which can make consumers repeat the same update.

Use the element itself as a stable event listener so reconnecting does not register another anonymous callback. The regression checks exact checked/unchecked payload counts after two reconnections.

Validation: the regression first received three events instead of one; all 6 Chromium tests now pass through the repository's Karma runner. The TypeScript/declaration build, Rollup bundle, and full ESLint check pass using the installed lockfile dependencies on Node 24. The Windows cleanup wrapper was bypassed by running the same tools directly; Firefox and WebKit were not run.

[Copilot]

🟢 Approval recommended

Stable listener identity prevents duplicate registrations, and the regression verifies both checkbox states after repeated reconnections.

No open issues 🎉

What changed in this PR

Prevents duplicate task-lists-check events when a <task-lists> element reconnects.

Changes:

• Uses the element itself as a stable change listener.
• Adds regression coverage for checked and unchecked payloads after two reconnections.

File	Description
test/​test.js	Verifies exact event counts after reconnecting.
src/​task-lists-element.ts	Replaces the anonymous listener with handleEvent.

_{Review effort: Max}