Rewrite Next, ESLint, PostCSS, and tsconfig overlay.

CSP, login/register redirects, pdfjs-dist externals, and canvas alias stay the same. package.json is unchanged.

tests/test_periscope_frontend_next_config_rewrite.py

@@ -0,0 +1,40 @@
+"""Frontend Next/ESLint/PostCSS overlay lives under periscope/src."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+SRC = ROOT / "periscope" / "src" / "frontend"
+
+
+def test_next_and_eslint_are_src():
+    for rel in ("next.config.ts", "eslint.config.mjs", "postcss.config.mjs", "tsconfig.json"):
+        path = SRC / rel
+        assert path.is_file(), rel
+        assert "Native Periscope overlay" not in path.read_text(encoding="utf-8")[:400]
+
+
+def test_next_config_keeps_runtime_contract():
+    text = (SRC / "next.config.ts").read_text(encoding="utf-8")
+    assert 'from "./src/lib/csp-hosts"' in text
+    assert 'allowedDevOrigins: ["127.0.0.1", "localhost"]' in text
+    assert 'serverExternalPackages: ["pdfjs-dist"]' in text
+    assert 'canvas: { browser: "" }' in text
+    assert 'source: "/login"' in text
+    assert 'destination: "/sign-in"' in text
+    assert 'source: "/register"' in text
+    assert 'destination: "/sign-up"' in text
+    assert "X-Content-Type-Options" in text
+    assert "X-Frame-Options" in text
+    assert "Strict-Transport-Security" in text
+    assert "Content-Security-Policy" in text
+    assert "worker-src 'self' blob:" in text
+    assert "pdfjs-dist" in text
+
+
+def test_eslint_uses_next_core_web_vitals():
+    text = (SRC / "eslint.config.mjs").read_text(encoding="utf-8")
+    assert "eslint-config-next/core-web-vitals" in text
+    assert "eslint-config-next/typescript" in text
+    assert ".next/**" in text