fix(swap): find oob targets in the document when the context element is detached

[yfwmaniish]

Fixes #3959.

What

swap() picks the rootNode used for hx-swap-oob target lookup by calling getRootNode() on the request's contextElement (the element that issued it):

const rootNode = swapOptions.contextElement ? getRootNode(swapOptions.contextElement, false) : getDocument()

That's correct while contextElement is still in the document - it's exactly what #2846 needed to make OOB swaps work inside shadow roots. But if contextElement has since been detached (its own region re-rendered while the request was in flight - e.g. a row in a list whose own hx-get is pending when the list itself gets replaced), elt.getRootNode() on a detached node returns its orphaned subtree's own root, not the document. oobSwap()'s querySelectorAllExt(rootNode, selector, false) then searches that orphaned root and finds nothing, so every OOB fragment in the response gets silently dropped (htmx:oobErrorNoTarget in the console is the only sign) - even though its target is still live in the document, and even though the response's main swap applies normally.

Fix

const rootNode = (swapOptions.contextElement && swapOptions.contextElement.isConnected)
  ? getRootNode(swapOptions.contextElement, false)
  : getDocument()

Falls back to the document when contextElement is disconnected, leaving the connected-trigger / shadow-root behavior #2846 added completely untouched.

Testing

• Added a test to test/attributes/hx-swap-oob.js: click a trigger, detach it (.remove()) before the response lands, and assert a separate, still-in-document OOB target still receives its content.
• Negative control: reverted just src/htmx.js, kept the test - it fails with the target's innerHTML staying empty (the drop), all other 33 tests in the file still pass. Restored.
• Full suite: 848/848 passing (3 pre-existing skips, unrelated), including both existing shadow-DOM OOB tests from fix for hx-swab-oob within web components #2846 - confirming the connected/shadow-root case is untouched.
• eslint clean on both changed files.

PR targets dev per CONTRIBUTING.md.

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