Rewrite datasheet PDF sheet overlay.

Right-side Sheet still mounts PdfViewerPanel only while open; shadcn Sheet stays imported.

tests/test_periscope_frontend_pdf_sheet_rewrite.py

@@ -0,0 +1,18 @@
+"""Datasheet PDF sheet overlay lives under periscope/src."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+SRC = ROOT / "periscope" / "src" / "frontend" / "src"
+
+
+def test_pdf_sheet_is_src():
+    path = SRC / "components/pdf/pdf-viewer-sheet.tsx"
+    text = path.read_text(encoding="utf-8")
+    assert "Native Periscope overlay" not in text[:400]
+    assert "export function PdfViewerSheet" in text
+    assert "PdfViewerPanel" in text
+    assert 'side="right"' in text
+    assert "sr-only" in text