fix: gate skills by OS

src/agents/skills.ts

@@ -27,6 +27,7 @@ export type ClawdisSkillMetadata = {
   primaryEnv?: string;
   emoji?: string;
   homepage?: string;
+  os?: string[];
   requires?: {
     bins?: string[];
     env?: string[];
@@ -188,6 +189,10 @@ export function resolveSkillsInstallPreferences(
   return { preferBrew, nodeManager };
 }
 
+export function resolveRuntimePlatform(): string {
+  return process.platform;
+}
+
 export function resolveConfigPath(
   config: ClawdisConfig | undefined,
   pathStr: string,
@@ -280,6 +285,7 @@ function resolveClawdisMetadata(
     const install = installRaw
       .map((entry) => parseInstallSpec(entry))
       .filter((entry): entry is SkillInstallSpec => Boolean(entry));
+    const osRaw = normalizeStringList(clawdisObj.os);
     return {
       always:
         typeof clawdisObj.always === "boolean" ? clawdisObj.always : undefined,
@@ -297,6 +303,7 @@ function resolveClawdisMetadata(
         typeof clawdisObj.primaryEnv === "string"
           ? clawdisObj.primaryEnv
           : undefined,
+      os: osRaw.length > 0 ? osRaw : undefined,
       requires: requiresRaw
         ? {
             bins: normalizeStringList(requiresRaw.bins),
@@ -323,9 +330,13 @@ function shouldIncludeSkill(params: {
   const skillKey = resolveSkillKey(entry.skill, entry);
   const skillConfig = resolveSkillConfig(config, skillKey);
   const allowBundled = normalizeAllowlist(config?.skills?.allowBundled);
+  const osList = entry.clawdis?.os ?? [];
 
   if (skillConfig?.enabled === false) return false;
   if (!isBundledSkillAllowed(entry, allowBundled)) return false;
+  if (osList.length > 0 && !osList.includes(resolveRuntimePlatform())) {
+    return false;
+  }
   if (entry.clawdis?.always === true) {
     return true;
   }