feat: sync shared skills contract and graph-first discipline

app/api/skills/route.ts

@@ -1,5 +1,5 @@
-import { NextResponse } from 'next/server';
-import { listSkills } from '@/services/skills/skillService';
+import { NextRequest, NextResponse } from 'next/server';
+import { listSkills, writeSkill } from '@/services/skills/skillService';
 
 export const runtime = 'nodejs';
 
@@ -15,3 +15,44 @@ export async function GET() {
     );
   }
 }
+
+export async function POST(request: NextRequest) {
+  try {
+    const body = await request.json();
+    const name = typeof body?.name === 'string' ? body.name.trim() : '';
+    const content = typeof body?.content === 'string' ? body.content : '';
+
+    if (!name) {
+      return NextResponse.json(
+        { success: false, error: 'Skill name is required' },
+        { status: 400 }
+      );
+    }
+
+    if (!content.trim()) {
+      return NextResponse.json(
+        { success: false, error: 'Skill content is required' },
+        { status: 400 }
+      );
+    }
+
+    const result = writeSkill(name, content);
+    if (!result.success) {
+      return NextResponse.json(
+        { success: false, error: result.error || 'Failed to write skill' },
+        { status: 400 }
+      );
+    }
+
+    return NextResponse.json({
+      success: true,
+      message: `Skill "${name}" saved`,
+    });
+  } catch (error) {
+    console.error('[API /skills POST] error:', error);
+    return NextResponse.json(
+      { success: false, error: error instanceof Error ? error.message : 'Failed to write skill' },
+      { status: 500 }
+    );
+  }
+}