chore: update vendored skills and record provenance

humanizer 2.2.0 -> 2.9.1 (blader/humanizer, MIT): adds a Voice
Calibration section and a passive-voice pattern, reworks negative
parallelisms and em dashes. Version moved to metadata.version upstream.

impeccable 3.6.0 -> 4.0.4 (pbakaus/impeccable, Apache-2.0): the repo
tags the skill and the npm CLI separately, so 3.6.0 was a real release
and npm's 3.5.0 was never the comparison. Adds native-platform reference
briefs.

Each now carries an UPSTREAM file; bin/check-vendored.sh reports drift.

skills/impeccable/scripts/lib/design-parser.mjs

@@ -62,7 +62,7 @@ function parseYamlSubset(yaml) {
       stack.pop();
     }
 
-    const key = content.slice(0, colonIdx).trim();
+    const key = unquoteYamlKey(content.slice(0, colonIdx).trim());
     const rest = stripInlineYamlComment(content.slice(colonIdx + 1).trim());
     const parent = stack[stack.length - 1].obj;
 
@@ -93,6 +93,13 @@ function findTopLevelColon(s) {
   return -1;
 }
 
+function unquoteYamlKey(key) {
+  if ((key.startsWith('"') && key.endsWith('"')) || (key.startsWith("'") && key.endsWith("'"))) {
+    return key.slice(1, -1);
+  }
+  return key;
+}
+
 function stripInlineYamlComment(s) {
   let inQuote = null;
   for (let i = 0; i < s.length; i++) {