Fix x-ref crash during child-element morph

[calebporzio]

Summary

• Fixes TypeError: Cannot read property '_x_refs' of undefined when calling Alpine.morph() on a child element (not the x-data root) that contains x-ref attributes
• Wraps x-ref's inline handler with skipDuringClone() — the established Alpine pattern used by 10+ other directives
• Adds Cypress test that morphs a child <section> containing x-ref and verifies state preservation + ref resolution

Problem

When morphing a child element, morph's cloneNode() runs directives on detached to elements whose parent chain has no [x-data] ancestor. closestRoot() returns undefined, and x-ref dereferences it → crash.

This affects htmx+Alpine users in production (reported in #3797, #3758, #3003).

Why skipDuringClone over a null guard

The PR #4744 proposed if (! root) return — a valid fix, but skipDuringClone is the Alpine-established pattern for "this directive doesn't need to run during clone." Refs on detached to elements are discarded anyway; post-morph, refs re-register on live DOM via the MutationObserver path.

Test plan

• New test: morph child element with x-ref — no crash, state preserved, $refs resolves
• All 35 morph tests pass
• All 6 $refs tests pass
• All 4 clone tests pass

Closes #3797. Alternative to #4744.

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