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>

market/queries.sx

@@ -7,8 +7,10 @@
 
 (defquery products-by-ids (&key ids)
   "Return product details for comma-separated IDs."
-  (service "market-data" "products-by-ids" :ids (split-ids ids)))
+  (service "market-data" "products-by-ids"
+    :ids (map parse-int (filter (fn (s) (not (empty? s))) (split (str ids) ",")))))
 
 (defquery marketplaces-by-ids (&key ids)
   "Return marketplace data for comma-separated IDs."
-  (service "market-data" "marketplaces-by-ids" :ids (split-ids ids)))
+  (service "market-data" "marketplaces-by-ids"
+    :ids (map parse-int (filter (fn (s) (not (empty? s))) (split (str ids) ",")))))