Pkldoc generates broken page anchors

Searching the standard library docs, I noticed that I always land at the top of the page, not at the function I search for. For example, searching for `sort` takes me to `https://pkl-lang.org/package-docs/pkl/current/base/Collection.html#sort()`. But `#sort()` doesn't exist, so I land at the top of the page. Inspecting the page source, I found that `id` attributes are erroneously percent-encoded:
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Reproduce the problem by opening the standard-library documentation URL for Collection.sort() and inspect the generated HTML around its anchor. Trace how pkldoc produces the percent-encoded id, then verify that the generated link resolves directly to the sort function instead of the top of the page.

Written by the indexing model from the issue text.