fix: support textContent swap style for hx-swap-oob (#3563)

[manwithacat]

Fixes #3563.

The bug

swapWithStyle() (src/htmx.js:1799) has cases for every OOB swap style — none, outerHTML, afterbegin, beforebegin, beforeend, afterend, delete — but no case for textContent. Falling into the default branch eventually recurses with htmx.config.defaultSwapStyle (normally innerHTML), so an hx-swap-oob="textContent" swap silently behaves like an innerHTML swap.

This contradicts the documented textContent contract — hx-swap docs say:

textContent — Replace the text content of the target element, without parsing the response as HTML.

The primary-swap path already handles this correctly at src/htmx.js:1907 (target.textContent = content, before any HTML parsing). The OOB path was the outlier.

The fix

Add a case 'textContent' to swapWithStyle mirroring the primary-swap behavior:

case 'textContent':
  target.textContent = fragment.textContent
  return

For non-inline OOB swaps, oobSwap() sets fragment to the parsed OOB element clone (line 1492), so fragment.textContent is the concatenated text of all descendants — matching the OOB doc rule that "the encapsulating tag pair will be stripped for all strategies other than outerHTML".

3 lines in src/htmx.js.

Tests

Two new cases in test/attributes/hx-swap-oob.js:

1. handles textContent response properly — verifies <h1>Swapped</h1> inside an OOB element becomes literal text Swapped in the target, not a parsed <h1> element.
2. handles textContent oob swap with selector — verifies the textContent:#selector form works the same way.

Both fail before the fix (the <h1> is parsed and inserted as an element), pass after.

Full suite: 848 passed, 0 failed, 3 skipped, 99.9% coverage. ESLint clean.

Live before/after demo

https://manwithacat.github.io/htmx/demos/hx-swap-oob-textContent/

Side-by-side iframes load the same base commit (d53932d4) with and without this 3-line patch, using a mock XMLHttpRequest so htmx runs its real lifecycle without needing a server. The buggy panel renders the OOB response's <h1> as a real DOM element; the fixed panel renders it as literal text.

Notes for reviewers

• I did not add cleanUpElement() calls for removed children before assigning target.textContent. The primary-swap textContent path at src/htmx.js:1908 doesn't either, and adding cleanup only on the OOB side would be inconsistent. Happy to follow up with a separate PR that adds it to both paths if that's wanted.
• No docs change needed — hx-swap.md already lists textContent and hx-swap-oob.md already says any valid hx-swap value works. The docs were correct; the code was the outlier.