🐛 fix(markdown): drop whitespace in link destinations

[gaborbernat]

to_markdown copied a tab or line break in a link or image destination into the Markdown. <a href="a\nb">x</a> became [x](a\nb), which reads back as literal text, since no destination form holds a line ending (CommonMark 6.3).

The URL parser removes every tab and newline from a URL (URL Standard, basic URL parser), so a\nb and ab name the same URL. The destination writer now leaves them out before it picks the bare or the <...> form, giving [x](ab).

markdownify 1.2.3 and html2text 2025.4.15 both write [x](a\nb).

[codspeed]

Merging this PR will regress 1 benchmark

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 579 untouched benchmarks
⏩ 32 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	test_feature[prune-shared-single]	89.1 µs	96.1 µs	-7.31%
⚡	test_feature[shadow-slot-comments]	137.9 µs	83.2 µs	+65.74%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing gaborbernat:fix/markdown-url-whitespace (0c37ec5) with main (af31f20)}

Footnotes

1. 32 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩