Clip-path URLs with absolute same-document references break in exported images

Expected Behavior

When exporting SVG/HTML content with html-to-image, clip-path references that point to the same document using absolute URLs should continue to work after DOM cloning.

Examples that should behave equivalently in export output:

• url("https://current-host/context.html#clip1")
• url("/context.html#clip1")
• url("#clip1")

All of these should resolve to the local cloned definition (effectively url(#clip1)).

Current Behavior

During export, absolute same-document clip-path URLs are not consistently resolved in the cloned tree.
As a result, clipping is lost or elements disappear in the generated image.

This affects clip-path when defined via:

• SVG presentation attribute (clip-path="url(...)")
• Inline style (style="clip-path: url(...)")

Possible Solution

Normalize clip-path URL values during clone/decorate:

• Detect url(...) clip-path values
• If URL points to current document with hash fragment, rewrite to local fragment form url(#id)
• Keep external references unchanged

Apply this normalization for attribute and inline style.

Steps To Reproduce

1. Create an SVG with <clipPath id="clip1">...</clipPath>.
2. Apply clip-path with absolute same-document URL (for example url('/context.html#clip1')) via CSS, inline style, or SVG attribute.
3. Export the node with html-to-image (toPng/toSvg).
4. Compare output with browser rendering of original DOM.

No runtime exception in many cases.
Observed symptom is incorrect rendering: clip-path is not applied in exported image.