refactor(pure): remove duplicate regex and dead empty-string guard

src/pure.js

@@ -11,15 +11,12 @@ export function parseTarget(input) {
   if (typeof input !== 'string') return null;
 
   const cleaned = input.replace(/,/g, '').trim().toLowerCase();
-  if (cleaned === '') return null;
-
-  // Reject anything other than digits, optional decimal, and optional single trailing suffix letter
-  if (!/^\d+(\.\d+)?[kmbt]?$/.test(cleaned)) return null;
 
   const match = cleaned.match(/^(\d+(?:\.\d+)?)([kmbt])?$/);
   if (!match) return null;
 
   const num = parseFloat(match[1]);
+  // regex permits '0'; reject it
   if (!Number.isFinite(num) || num <= 0) return null;
 
   const suffix = match[2];

tests/pure.test.js

@@ -30,4 +30,5 @@ test('parseTarget: rejects invalid input', () => {
   assert.equal(parseTarget(undefined), null);
   assert.equal(parseTarget('25M.5'), null);
   assert.equal(parseTarget('1.5.5M'), null);
+  assert.equal(parseTarget('0'), null);
 });