fix: eslint findings

Remove dead code and unused imports, drop useless assignments, and tune
rules in eslint.config.js (underscore-prefixed unused names, intentional BOM/NBSP,
React Compiler rules from eslint-plugin-react-hooks 7 as warnings).

scripts/decor/script-word.mjs

@@ -52,7 +52,6 @@ function wordCommands(font) {
 function rotate(cmds) {
   const pts = cmds.flatMap((c) => c.args);
   const xs = pts.filter((_, i) => i % 2 === 0);
-  const ys = pts.filter((_, i) => i % 2 === 1);
   const inkLen = Math.max(...xs) - Math.min(...xs);
   const s = INK_LENGTH / inkLen;
   const map = (x, y) => [-y * s, -x * s];