feat: add skill path resolution with shadowing support

lib/skills-core.js

@@ -95,7 +95,51 @@ function findSkillsInDir(dir, sourceType, maxDepth = 3) {
     return skills;
 }
 
+/**
+ * Resolve a skill name to its file path, handling shadowing
+ * (personal skills override superpowers skills).
+ *
+ * @param {string} skillName - Name like "superpowers:brainstorming" or "my-skill"
+ * @param {string} superpowersDir - Path to superpowers skills directory
+ * @param {string} personalDir - Path to personal skills directory
+ * @returns {{skillFile: string, sourceType: string, skillPath: string} | null}
+ */
+function resolveSkillPath(skillName, superpowersDir, personalDir) {
+    // Strip superpowers: prefix if present
+    const forceSuperpowers = skillName.startsWith('superpowers:');
+    const actualSkillName = forceSuperpowers ? skillName.replace(/^superpowers:/, '') : skillName;
+
+    // Try personal skills first (unless explicitly superpowers:)
+    if (!forceSuperpowers && personalDir) {
+        const personalPath = path.join(personalDir, actualSkillName);
+        const personalSkillFile = path.join(personalPath, 'SKILL.md');
+        if (fs.existsSync(personalSkillFile)) {
+            return {
+                skillFile: personalSkillFile,
+                sourceType: 'personal',
+                skillPath: actualSkillName
+            };
+        }
+    }
+
+    // Try superpowers skills
+    if (superpowersDir) {
+        const superpowersPath = path.join(superpowersDir, actualSkillName);
+        const superpowersSkillFile = path.join(superpowersPath, 'SKILL.md');
+        if (fs.existsSync(superpowersSkillFile)) {
+            return {
+                skillFile: superpowersSkillFile,
+                sourceType: 'superpowers',
+                skillPath: actualSkillName
+            };
+        }
+    }
+
+    return null;
+}
+
 module.exports = {
     extractFrontmatter,
-    findSkillsInDir
+    findSkillsInDir,
+    resolveSkillPath
 };