Refactor SX primitives: modular, isomorphic, general-purpose

Spec modularization:
- Add (define-module :name) markers to primitives.sx creating 11 modules
  (7 core, 4 stdlib). Bootstrappers can now selectively include modules.
- Add parse_primitives_by_module() to boundary_parser.py.
- Remove split-ids primitive; inline at 4 call sites in blog/market queries.

Python file split:
- primitives.py: slimmed to registry + core primitives only (~350 lines)
- primitives_stdlib.py: NEW — stdlib primitives (format, text, style, debug)
- primitives_ctx.py: NEW — extracted 12 page context builders from IO
- primitives_io.py: add register_io_handler decorator, auto-derive
  IO_PRIMITIVES from registry, move sync IO bridges here

JS parity fixes:
- = uses === (strict equality), != uses !==
- round supports optional ndigits parameter
- concat uses nil-check not falsy-check (preserves 0, "", false)
- escape adds single quote entity (') matching Python/markupsafe
- assert added (was missing from JS entirely)

Bootstrapper modularization:
- PRIMITIVES_JS_MODULES / PRIMITIVES_PY_MODULES dicts keyed by module
- --modules CLI flag for selective inclusion (core.* always included)
- Regenerated sx-ref.js and sx_ref.py with all fixes

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

shared/sx/primitives_stdlib.py

@@ -0,0 +1,131 @@
+"""
+Standard library primitives — isomorphic, opt-in modules.
+
+Augment core with format, text, style, and debug primitives.
+These are registered into the same _PRIMITIVES registry as core.
+"""
+from __future__ import annotations
+
+from typing import Any
+
+from .primitives import register_primitive
+from .types import NIL
+
+
+# ---------------------------------------------------------------------------
+# stdlib.format
+# ---------------------------------------------------------------------------
+
+@register_primitive("format-date")
+def prim_format_date(date_str: Any, fmt: str) -> str:
+    """``(format-date date-str fmt)`` → formatted date string."""
+    from datetime import datetime
+    try:
+        dt = datetime.fromisoformat(str(date_str))
+        return dt.strftime(fmt)
+    except (ValueError, TypeError):
+        return str(date_str) if date_str else ""
+
+
+@register_primitive("format-decimal")
+def prim_format_decimal(val: Any, places: Any = 2) -> str:
+    """``(format-decimal val places)`` → formatted decimal string."""
+    try:
+        return f"{float(val):.{int(places)}f}"
+    except (ValueError, TypeError):
+        return "0." + "0" * int(places)
+
+
+@register_primitive("parse-int")
+def prim_parse_int(val: Any, default: Any = 0) -> int | Any:
+    """``(parse-int val default?)`` → int(val) with fallback."""
+    try:
+        return int(val)
+    except (ValueError, TypeError):
+        return default
+
+
+@register_primitive("parse-datetime")
+def prim_parse_datetime(val: Any) -> Any:
+    """``(parse-datetime "2024-01-15T10:00:00")`` → ISO string or nil."""
+    from datetime import datetime
+    if not val or val is NIL:
+        return NIL
+    try:
+        dt = datetime.fromisoformat(str(val))
+        return dt.isoformat()
+    except (ValueError, TypeError):
+        return NIL
+
+
+# ---------------------------------------------------------------------------
+# stdlib.text
+# ---------------------------------------------------------------------------
+
+@register_primitive("pluralize")
+def prim_pluralize(count: Any, singular: str = "", plural: str = "s") -> str:
+    """``(pluralize count)`` → "s" if count != 1, else "".
+    ``(pluralize count "item" "items")`` → "item" or "items"."""
+    try:
+        n = int(count)
+    except (ValueError, TypeError):
+        n = 0
+    if singular or plural != "s":
+        return singular if n == 1 else plural
+    return "" if n == 1 else "s"
+
+
+@register_primitive("escape")
+def prim_escape(s: Any) -> str:
+    """``(escape val)`` → HTML-escaped string."""
+    from markupsafe import escape as _escape
+    return str(_escape(str(s) if s is not None and s is not NIL else ""))
+
+
+@register_primitive("strip-tags")
+def prim_strip_tags(s: str) -> str:
+    """Strip HTML tags from a string."""
+    import re
+    return re.sub(r"<[^>]+>", "", s)
+
+
+# ---------------------------------------------------------------------------
+# stdlib.style
+# ---------------------------------------------------------------------------
+
+@register_primitive("css")
+def prim_css(*args: Any) -> Any:
+    """``(css :flex :gap-4 :hover:bg-sky-200)`` → StyleValue."""
+    from .types import Keyword
+    from .style_resolver import resolve_style
+    atoms = tuple(
+        (a.name if isinstance(a, Keyword) else str(a))
+        for a in args if a is not None and a is not NIL and a is not False
+    )
+    if not atoms:
+        return NIL
+    return resolve_style(atoms)
+
+
+@register_primitive("merge-styles")
+def prim_merge_styles(*styles: Any) -> Any:
+    """``(merge-styles style1 style2)`` → merged StyleValue."""
+    from .types import StyleValue
+    from .style_resolver import merge_styles
+    valid = [s for s in styles if isinstance(s, StyleValue)]
+    if not valid:
+        return NIL
+    if len(valid) == 1:
+        return valid[0]
+    return merge_styles(valid)
+
+
+# ---------------------------------------------------------------------------
+# stdlib.debug
+# ---------------------------------------------------------------------------
+
+@register_primitive("assert")
+def prim_assert(condition: Any, message: str = "Assertion failed") -> bool:
+    if not condition:
+        raise RuntimeError(f"Assertion error: {message}")
+    return True