Phase 8-9: Convert events + sx layouts, add missing JS primitives

Events (Phase 8):
- Create events/sx/layouts.sx with 18 defcomps for all 9 layout pairs
- Convert all layout functions to render_to_sx_with_env + _ctx_to_env
- Convert 5 render functions to eliminate root_header_sx calls
- Zero root_header_sx references remain in events

SX Docs (Phase 9):
- Create sx/sx/layouts.sx with layout defcomps
- Convert 4 layout functions to render_to_sx_with_env + _ctx_to_env

JS primitives:
- Add slice, replace, upper, lower, trim, escape, strip-tags, split,
  join, pluralize, clamp, parse-int, format-decimal, format-date,
  parse-datetime, split-ids, starts-with?, ends-with?, dissoc, into
- Fix contains? for strings (indexOf instead of in operator)
- Prevents "Undefined symbol" errors when .sx expressions using
  server-side primitives are evaluated client-side

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sx/sxc/pages/__init__.py

@@ -3061,28 +3061,31 @@ def _register_sx_layouts() -> None:
 
 async def _sx_full_headers(ctx: dict, **kw: Any) -> str:
     """Full headers for sx home page: root + sx menu row."""
-    from shared.sx.helpers import root_header_sx
+    from shared.sx.helpers import render_to_sx_with_env, _ctx_to_env
+    from shared.sx.parser import SxExpr
 
     main_nav = await _main_nav_sx(kw.get("section"))
-    root_hdr = await root_header_sx(ctx)
     sx_row = await _sx_header_sx(main_nav)
-    return "(<> " + root_hdr + " " + sx_row + ")"
+    return await render_to_sx_with_env("sx-layout-full", _ctx_to_env(ctx),
+        sx_row=SxExpr(sx_row))
 
 
 async def _sx_oob_headers(ctx: dict, **kw: Any) -> str:
     """OOB headers for sx home page."""
-    from shared.sx.helpers import root_header_sx, oob_header_sx
+    from shared.sx.helpers import render_to_sx_with_env, _ctx_to_env, oob_header_sx
+    from shared.sx.parser import SxExpr
 
-    root_hdr = await root_header_sx(ctx)
     main_nav = await _main_nav_sx(kw.get("section"))
     sx_row = await _sx_header_sx(main_nav)
-    rows = "(<> " + root_hdr + " " + sx_row + ")"
+    rows = await render_to_sx_with_env("sx-layout-full", _ctx_to_env(ctx),
+        sx_row=SxExpr(sx_row))
     return await oob_header_sx("root-header-child", "sx-header-child", rows)
 
 
 async def _sx_section_full_headers(ctx: dict, **kw: Any) -> str:
     """Full headers for sx section pages: root + sx row + sub row."""
-    from shared.sx.helpers import root_header_sx
+    from shared.sx.helpers import render_to_sx_with_env, _ctx_to_env
+    from shared.sx.parser import SxExpr
 
     section = kw.get("section", "")
     sub_label = kw.get("sub_label", section)
@@ -3090,16 +3093,17 @@ async def _sx_section_full_headers(ctx: dict, **kw: Any) -> str:
     sub_nav = kw.get("sub_nav", "")
     selected = kw.get("selected", "")
 
-    root_hdr = await root_header_sx(ctx)
     main_nav = await _main_nav_sx(section)
     sub_row = await _sub_row_sx(sub_label, sub_href, sub_nav, selected)
     sx_row = await _sx_header_sx(main_nav, child=sub_row)
-    return "(<> " + root_hdr + " " + sx_row + ")"
+    return await render_to_sx_with_env("sx-section-layout-full", _ctx_to_env(ctx),
+        sx_row=SxExpr(sx_row))
 
 
 async def _sx_section_oob_headers(ctx: dict, **kw: Any) -> str:
     """OOB headers for sx section pages."""
-    from shared.sx.helpers import root_header_sx, oob_header_sx
+    from shared.sx.helpers import render_to_sx_with_env, _ctx_to_env, oob_header_sx
+    from shared.sx.parser import SxExpr
 
     section = kw.get("section", "")
     sub_label = kw.get("sub_label", section)
@@ -3107,11 +3111,11 @@ async def _sx_section_oob_headers(ctx: dict, **kw: Any) -> str:
     sub_nav = kw.get("sub_nav", "")
     selected = kw.get("selected", "")
 
-    root_hdr = await root_header_sx(ctx)
     main_nav = await _main_nav_sx(section)
     sub_row = await _sub_row_sx(sub_label, sub_href, sub_nav, selected)
     sx_row = await _sx_header_sx(main_nav, child=sub_row)
-    rows = "(<> " + root_hdr + " " + sx_row + ")"
+    rows = await render_to_sx_with_env("sx-section-layout-full", _ctx_to_env(ctx),
+        sx_row=SxExpr(sx_row))
     return await oob_header_sx("root-header-child", "sx-header-child", rows)