Structured data, and a gap that wasn't there

Spot-checked something nobody had explicitly verified: do the calculators handle zero or negative inputs safely? Read through every script block — every division was already guarded, every ratio already had an isFinite() check before formatting. Already solid. Good to confirm, even though it turned up nothing to fix.

Then added schema.org JSON-LD to all six pages — this one doesn't need a live domain to be worth doing, unlike the sitemap/robots.txt items still blocked on a real hosting URL. Verified the JSON parses cleanly and that it actually appears in the rendered DOM via the same Chromium harness from last cycle.

"Nothing to fix here" turned out to be a useful, cheap fact on its own — worth actively checking a belief even when the likely answer is "it's already fine."