fix: make skill/template discovery dynamic

Replace hardcoded SKILL_FILES and TEMPLATES arrays in skill-check.ts,
gen-skill-docs.ts, and dev-skill.ts with a shared discover-skills.ts
utility that scans the filesystem. New skills are now picked up
automatically without updating three separate lists.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/discover-skills.ts

@@ -0,0 +1,39 @@
+/**
+ * Shared discovery for SKILL.md and .tmpl files.
+ * Scans root + one level of subdirs, skipping node_modules/.git/dist.
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+
+const SKIP = new Set(['node_modules', '.git', 'dist']);
+
+function subdirs(root: string): string[] {
+  return fs.readdirSync(root, { withFileTypes: true })
+    .filter(d => d.isDirectory() && !SKIP.has(d.name))
+    .map(d => d.name);
+}
+
+export function discoverTemplates(root: string): Array<{ tmpl: string; output: string }> {
+  const dirs = ['', ...subdirs(root)];
+  const results: Array<{ tmpl: string; output: string }> = [];
+  for (const dir of dirs) {
+    const rel = dir ? `${dir}/SKILL.md.tmpl` : 'SKILL.md.tmpl';
+    if (fs.existsSync(path.join(root, rel))) {
+      results.push({ tmpl: rel, output: rel.replace(/\.tmpl$/, '') });
+    }
+  }
+  return results;
+}
+
+export function discoverSkillFiles(root: string): string[] {
+  const dirs = ['', ...subdirs(root)];
+  const results: string[] = [];
+  for (const dir of dirs) {
+    const rel = dir ? `${dir}/SKILL.md` : 'SKILL.md';
+    if (fs.existsSync(path.join(root, rel))) {
+      results.push(rel);
+    }
+  }
+  return results;
+}