fix: skip patching focused input/textarea elements during DOM update

[adnaan]

Problem

When the server re-renders a textarea (or input) that the user is actively typing in, the client's DOM patcher replaces the element's content, causing:

1. Cursor resets to position 0 — each patch moves the cursor to the start
2. Reversed text — typing "hello" renders as "olleh" because each character is inserted at position 0 after the cursor reset
3. Content wipe — on form submit, the patched content may be stale or empty

This makes Change() method (live-as-you-type updates) unusable with textareas.

Expected behavior

Phoenix LiveView's client skips patching form elements that have focus. The focused element's value is left untouched during the DOM diff/patch cycle. Only unfocused elements are updated.

Reproduction

1. Create a controller with a Change() method that reads a textarea value
2. The template has <textarea name="content">{{.Content}}</textarea>
3. Type in the textarea — each keystroke triggers Change() → server re-renders → client patches textarea → cursor resets

Proposed fix

In the DOM patcher, before updating an element's text content or value:

• Check if the element is document.activeElement
• If it is, skip the update (the user's local state is authoritative while they're typing)
• Only apply server-sent values to unfocused elements

This matches LiveView's behavior and enables Change()-based live preview patterns.

[adnaan]

The fix (shouldSkipUpdate + textarea value sync in onElUpdated) is implemented in the fix/skip-focused-element-patch branch but doesn't appear to be published to npm yet. The unpkg.com CDN still serves the old client without the fix. The live-preview example's cursor reversal is caused by this — once the fix is published to npm, it should work.

[adnaan]

The v0.8.8 release (PR #32) uses the value-copy approach (toEl.value = fromEl.value) but does NOT skip the morphdom update. Morphdom still patches the element's text node child, which resets the cursor position.

The correct fix from the fix/skip-focused-element-patch branch uses shouldSkipUpdate(fromEl) → return false which skips the entire morphdom update for focused elements. This branch needs to be merged and a v0.8.9 published.

The value-copy approach is insufficient because:

1. Morphdom replaces the text node child (resets cursor to 0)
2. The value is set correctly but the cursor is already at position 0
3. Each keystroke inserts at position 0 → text appears reversed