Floor (not round) the post-filter totals in HTML report

When a user filters the file table, the totals row re-renders via
updateTotalsCell, which used Float#toFixed(2) — rounding 763/777
to 98.20%. The initial render uses fmtPct, which floors. Switch the
filter-update path to fmtPct so a user who sets minimum_coverage to
the displayed number doesn't get a failing run on the next pass.

Resolves #1115.

Author: sferik

html_frontend/src/app.ts

@@ -719,7 +719,7 @@ function updateCoverageCells(
   const p = (covered * 100.0) / total;
   const cls = pctClass(p);
   if (covCell) {
-    covCell.innerHTML = `<div class="coverage-cell">${renderCoverageBar(p)}<span class="coverage-pct">${p.toFixed(2)}%</span></div>`;
+    covCell.innerHTML = `<div class="coverage-cell">${renderCoverageBar(p)}<span class="coverage-pct">${fmtPct(p)}%</span></div>`;
     covCell.className = `${covCell.className.replace(/green|yellow|red/g, '').trim()} ${cls}`;
   }
   if (numEl) numEl.textContent = fmtNum(covered) + '/';