Add hub iframe embed shell with tab fragment API.

Replace full-page soft nav with a persistent shell and /api/embed/page loads so tab switches in the hub iframe avoid document.write flicker.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/build_embed_fragment.py

@@ -0,0 +1,33 @@
+"""Build embed_page_fragment.html from gate index.html."""
+from __future__ import annotations
+
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent.parent
+src_lines = (ROOT / "crypto_monitor_gate" / "templates" / "index.html").read_text(
+    encoding="utf-8"
+).splitlines()
+
+# 1-based line numbers from index.html
+macro_body = src_lines[243:262]  # {% macro %} … {% endmacro %}
+grid_inner = src_lines[328:736]  # inside .grid (exclude outer wrapper)
+stats_block = src_lines[738:772]
+
+out_lines = [
+    "{# Hub iframe tab fragment — shared via embed_templates #}",
+    *macro_body,
+    '<div class="grid">',
+    *grid_inner,
+    "</div>",
+    *stats_block,
+]
+
+out_dir = ROOT / "embed_templates"
+out_dir.mkdir(exist_ok=True)
+text = "\n".join(out_lines) + "\n"
+text = text.replace(
+    "{% include 'order_monitor_rule_tips_gate.html' %}",
+    "{% include order_rule_tips_tpl %}",
+)
+(out_dir / "embed_page_fragment.html").write_text(text, encoding="utf-8")
+print("wrote", out_dir / "embed_page_fragment.html", "lines", len(out_lines))