fix(viewer): prevent column header placeholder truncation via min-width

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/static/view.js

@@ -76,6 +76,7 @@ document.addEventListener("DOMContentLoaded", () => {
         input.type = "text";
         input.className = "col-filter col-filter-text";
         input.placeholder = colName;
+        input.style.minWidth = `${colName.length + 1}ch`;
         input.setAttribute("aria-label", "filter " + colName);
         let debounceTimer;
         input.addEventListener("input", () => {