Fix CSP and hook ancestor discovery

Recognize Next.js 16 proxy files when detecting runtime CSP and mirror harness ancestor lookup when locating active hook manifests for nested projects.

AI assistance disclosure: Implemented and verified with Codex under maintainer direction.

tests/framework-fixtures/nextjs-proxy-csp/fixture.json

@@ -0,0 +1,15 @@
+{
+  "name": "Next.js 16 (proxy CSP)",
+  "config": {
+    "files": ["app/layout.tsx"],
+    "insertBefore": "</body>",
+    "commentSyntax": "jsx"
+  },
+  "sourceFiles": ["proxy.ts", "app/layout.tsx"],
+  "generatedFiles": [],
+  "wrapCases": [],
+  "csp": {
+    "shape": "middleware",
+    "signals": ["proxy.ts:Content-Security-Policy"]
+  }
+}