fix(link): unwrap stacked schemes split by whitespace in one pass [3.x]

[ManukMinasyan]

Problem

A domain-variant link that stacks http schemes with whitespace between them re-enters LinkFieldType::normalize() once per scheme. A 2,048 character value, the longest the item rule allows, takes about 250 passes and 47 ms. A host app that normalizes filter operands or import rows with this method pays that for every value.

A separator that trim() leaves in place, such as a non-breaking space or a zero-width space, also came back unparsed.

Change

The unwrap regex skips the whitespace between stacked schemes, using the same class the authority parse already strips. Every stacked form now resolves in at most two passes.

Measured

Value	Before	After
2,048 chars of http://	47 ms	0.7 ms
255 chars of the same	3.8 ms	0.24 ms
Normal URL	0.5 ms	0.5 ms

Tests

• A call-counting test over four separators (space, tab, non-breaking space, zero-width space) failed with 250 passes and passes with 2.
• A new case in the unparseable-links dataset pins the result for mixed separators.

No stored value changes shape, so no upgrade step is needed.

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