fix(parseProtocol): fix regex to require colon in protocol separator (#10729)

The regex used `(:?\/\/|:)` where `:?` was intended to be a
non-capturing group `(?:` but instead made the colon an optional
literal character. This caused URLs without a colon separator like
`http//example.com` to incorrectly match and return `http` as the
protocol. Fix the regex to `:(?:\/\/)?` which requires the colon
and optionally matches `//`, correctly rejecting malformed URLs.

Signed-off-by: Nikita Skovoroda <chalkerx@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Nikita Skovoroda <chalkerx@gmail.com>
Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/helpers/parseProtocol.js

@@ -1,6 +1,6 @@
 'use strict';
 
 export default function parseProtocol(url) {
-  const match = /^([-+\w]{1,25})(:?\/\/|:)/.exec(url);
+  const match = /^([-+\w]{1,25}):(?:\/\/)?/.exec(url);
   return (match && match[1]) || '';
 }

tests/unit/parseProtocol.test.js

@@ -25,4 +25,8 @@ describe('helpers::parseProtocol', () => {
       }
     );
   });
+
+  it('should not match URLs without a colon separator', () => {
+    assert.strictEqual(parseProtocol('http//example.com'), '');
+  });
 });