Rich text: use subscribeDelegatedListener for element event listeners

[ellatrix]

What?

Convert the remaining rich text event listeners from raw element.addEventListener to subscribeDelegatedListener, for consistency with the listeners already using it.

Why?

Most rich text listeners already use subscribeDelegatedListener (one shared listener per event type, dispatched along the target's ancestry). A handful still attach a listener per element. Unifying them is a small consistency/listener-count win, and prepares for multi-block selection on iOS where the editing host can be an ancestor of the element.

How?

• Converted input-rules, before-input-rules, input-events, insert-replacement-text, shortcuts, delete, undo-automatic-change, remove-browser-shortcuts, and the deprecated keydown in enter.
• Phase per listener: delegated listeners fire later (at the document) than the raw element listeners did, so listeners that must run before ancestor handlers (input-rules, before-input-rules, shortcuts, remove-browser-shortcuts, deprecated enter keydown) use capture; listeners that should let others preventDefault first or only observe (delete, undo-automatic-change, input-events, insert-replacement-text) stay bubble.
• firefox-compat is left as-is (focus does not bubble, so it cannot be delegated).

No behaviour change.

Testing Instructions

Type in a paragraph (Enter to split, Backspace to merge); use Markdown input rules (## , * , `code`); cut/copy/paste; undo an autocorrect; confirm Ctrl/Cmd+Z/Y still work. Everything should behave as before.

Testing Instructions for Keyboard

Covered above; all interactions are keyboard-driven.

Use of AI Tools

Drafted with Claude Code (Claude Opus 4.8) and reviewed before submitting.

🤖 Generated with Claude Code

[github-actions]

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[github-actions]

Size Change: +165 B (0%)

Total Size: 8.44 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	380 kB	+165 B (+0.04%)

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[github-actions]

Flaky tests detected in c789698.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/27214115706
📝 Reported issues:

• [Flaky Test] shouldn't conflict with server-side autosave #78706 in /test/e2e/specs/editor/various/autosave.spec.js