Separate core spec from web framework

Three-layer architecture:
  spec/  — Core language (19 files): evaluator, parser, primitives,
           CEK machine, types, continuations. Host-independent.
  web/   — Web framework (20 files): signals, adapters, engine,
           orchestration, boot, router, CSSX. Built on core spec.
  sx/    — Application (sx-docs website). Built on web framework.

Split boundary.sx into boundary-core.sx (type-of, make-env, identical?)
and boundary-web.sx (IO primitives, signals, spreads, page helpers).

Bootstrappers search spec/ → web/ → shared/sx/ref/ for .sx files.
Original files remain in shared/sx/ref/ as fallback during transition.
All 63 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/sx/ref/bootstrap_py.py

@@ -1325,9 +1325,17 @@ except ImportError:
     )
 
 
-def _parse_special_forms_spec(ref_dir: str) -> set[str]:
+def _parse_special_forms_spec(ref_dir: str, source_dirs=None) -> set[str]:
     """Parse special-forms.sx to extract declared form names."""
-    filepath = os.path.join(ref_dir, "special-forms.sx")
+    filepath = None
+    if source_dirs:
+        for d in source_dirs:
+            p = os.path.join(d, "special-forms.sx")
+            if os.path.exists(p):
+                filepath = p
+                break
+    if not filepath:
+        filepath = os.path.join(ref_dir, "special-forms.sx")
     if not os.path.exists(filepath):
         return set()
     with open(filepath) as f:
@@ -1359,9 +1367,9 @@ def _extract_eval_dispatch_names(all_sections: list) -> set[str]:
 
 
 def _validate_special_forms(ref_dir: str, all_sections: list,
-                            has_continuations: bool) -> None:
+                            has_continuations: bool, source_dirs=None) -> None:
     """Cross-check special-forms.sx against eval.sx dispatch. Warn on mismatches."""
-    spec_names = _parse_special_forms_spec(ref_dir)
+    spec_names = _parse_special_forms_spec(ref_dir, source_dirs=source_dirs)
     if not spec_names:
         return
 
@@ -1432,6 +1440,20 @@ def compile_ref_to_py(
                 prim_modules.append(m)
 
     ref_dir = os.path.dirname(os.path.abspath(__file__))
+    _project = os.path.abspath(os.path.join(ref_dir, "..", "..", ".."))
+    _source_dirs = [
+        os.path.join(_project, "spec"),
+        os.path.join(_project, "web"),
+        ref_dir,
+    ]
+
+    def _find_sx(filename):
+        for d in _source_dirs:
+            p = os.path.join(d, filename)
+            if os.path.exists(p):
+                return p
+        return None
+
     emitter = PyEmitter()
 
     # Resolve adapter set
@@ -1494,7 +1516,7 @@ def compile_ref_to_py(
     has_async = "async" in adapter_set
     if has_async:
         async_filename = ADAPTER_FILES["async"][0]
-        async_filepath = os.path.join(ref_dir, async_filename)
+        async_filepath = _find_sx(async_filename) or os.path.join(ref_dir, async_filename)
         if os.path.exists(async_filepath):
             with open(async_filepath) as f:
                 async_src = f.read()
@@ -1513,7 +1535,7 @@ def compile_ref_to_py(
 
     all_sections = []
     for filename, label in sx_files:
-        filepath = os.path.join(ref_dir, filename)
+        filepath = _find_sx(filename) or os.path.join(ref_dir, filename)
         if not os.path.exists(filepath):
             continue
         with open(filepath) as f:
@@ -1531,7 +1553,7 @@ def compile_ref_to_py(
     has_continuations = "continuations" in ext_set
 
     # Validate special forms
-    _validate_special_forms(ref_dir, all_sections, has_continuations)
+    _validate_special_forms(ref_dir, all_sections, has_continuations, source_dirs=_source_dirs)
 
     # Build output
     has_html = "html" in adapter_set

shared/sx/ref/run_js_sx.py

@@ -78,6 +78,13 @@ def compile_ref_to_js(
     from shared.sx.ref.sx_ref import evaluate
 
     ref_dir = _HERE
+    _PROJECT = os.path.abspath(os.path.join(_HERE, "..", "..", ".."))
+    # Source directories: core spec, web framework, and legacy ref (for bootstrapper tools)
+    _source_dirs = [
+        os.path.join(_PROJECT, "spec"),      # Core spec
+        os.path.join(_PROJECT, "web"),        # Web framework
+        ref_dir,                              # Legacy location (fallback)
+    ]
     env = load_js_sx()
 
     # Resolve adapter set
@@ -195,9 +202,16 @@ def compile_ref_to_js(
         parts.append(PLATFORM_CEK_JS)
 
     # Translate each spec file using js.sx
+    def _find_sx(filename):
+        for d in _source_dirs:
+            p = os.path.join(d, filename)
+            if os.path.exists(p):
+                return p
+        return None
+
     for filename, label in sx_files:
-        filepath = os.path.join(ref_dir, filename)
-        if not os.path.exists(filepath):
+        filepath = _find_sx(filename)
+        if not filepath:
             continue
         with open(filepath) as f:
             src = f.read()