Interactive reader feature

[bartveneman]

"See how your site compares" tool

Let a reader enter their own URL, analyze it live, and plot it against the
2027 dataset: show where they land on the report's percentile charts, and
in tables of pseudo-classes/elements/etc., mark which ones their own CSS
actually uses.

This would likely reuse Project Wallace's existing live site-analysis
capability (the core product) to analyze the entered URL on the fly, rather
than building new analysis infrastructure just for this.

This is exploratory — framed as "a crazy thought," not a committed feature.
Open questions:

• Scope: which charts/tables get this treatment — all of them, or a
  curated subset?
• Does it need its own dedicated page, or inline widgets spread throughout
  the report?
• Is it worth the build effort given everything else already planned for
  2027?