Phase 2: IO detection & selective expansion in deps.sx

Extend the spec with IO scanning functions (scan-io-refs, transitive-io-refs,
compute-all-io-refs, component-pure?) that detect IO primitive references in
component ASTs. Components are classified as pure (no IO deps, safe for client
rendering) or IO-dependent (must expand server-side).

The partial evaluator (_aser) now uses per-component IO metadata instead of
the global _expand_components toggle: IO-dependent components expand server-
side, pure components serialize for client. Layout slot context still expands
all components for backwards compat.

Spec: 5 new functions + 2 platform interface additions in deps.sx
Host: io_refs field + is_pure property on Component, compute_all_io_refs()
Bootstrap: both sx_ref.py and sx-ref.js updated with IO functions
Bundle analyzer: shows pure/IO classification per page

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

shared/static/scripts/sx-ref.js

@@ -609,6 +609,14 @@
     return result;
   }
 
+  function componentIoRefs(c) {
+    return c.ioRefs ? c.ioRefs.slice() : [];
+  }
+
+  function componentSetIoRefs(c, refs) {
+    c.ioRefs = refs;
+  }
+
 
   // =========================================================================
   // Platform interface — Parser
@@ -2456,6 +2464,43 @@ callExpr.push(dictGet(kwargs, k)); } }
   return classes;
 })(); };
 
+  // scan-io-refs-walk
+  var scanIoRefsWalk = function(node, ioNames, refs) { return (isSxTruthy((typeOf(node) == "symbol")) ? (function() {
+  var name = symbolName(node);
+  return (isSxTruthy(contains(ioNames, name)) ? (isSxTruthy(!contains(refs, name)) ? append_b(refs, name) : NIL) : NIL);
+})() : (isSxTruthy((typeOf(node) == "list")) ? forEach(function(item) { return scanIoRefsWalk(item, ioNames, refs); }, node) : (isSxTruthy((typeOf(node) == "dict")) ? forEach(function(key) { return scanIoRefsWalk(dictGet(node, key), ioNames, refs); }, keys(node)) : NIL))); };
+
+  // scan-io-refs
+  var scanIoRefs = function(node, ioNames) { return (function() {
+  var refs = [];
+  scanIoRefsWalk(node, ioNames, refs);
+  return refs;
+})(); };
+
+  // transitive-io-refs-walk
+  var transitiveIoRefsWalk = function(n, seen, allRefs, env, ioNames) { return (isSxTruthy(!contains(seen, n)) ? (append_b(seen, n), (function() {
+  var val = envGet(env, n);
+  return (isSxTruthy((typeOf(val) == "component")) ? (forEach(function(ref) { return (isSxTruthy(!contains(allRefs, ref)) ? append_b(allRefs, ref) : NIL); }, scanIoRefs(componentBody(val), ioNames)), forEach(function(dep) { return transitiveIoRefsWalk(dep, seen, allRefs, env, ioNames); }, scanRefs(componentBody(val)))) : (isSxTruthy((typeOf(val) == "macro")) ? (forEach(function(ref) { return (isSxTruthy(!contains(allRefs, ref)) ? append_b(allRefs, ref) : NIL); }, scanIoRefs(macroBody(val), ioNames)), forEach(function(dep) { return transitiveIoRefsWalk(dep, seen, allRefs, env, ioNames); }, scanRefs(macroBody(val)))) : NIL));
+})()) : NIL); };
+
+  // transitive-io-refs
+  var transitiveIoRefs = function(name, env, ioNames) { return (function() {
+  var allRefs = [];
+  var seen = [];
+  var key = (isSxTruthy(startsWith(name, "~")) ? name : (String("~") + String(name)));
+  transitiveIoRefsWalk(key, seen, allRefs, env, ioNames);
+  return allRefs;
+})(); };
+
+  // compute-all-io-refs
+  var computeAllIoRefs = function(env, ioNames) { return forEach(function(name) { return (function() {
+  var val = envGet(env, name);
+  return (isSxTruthy((typeOf(val) == "component")) ? componentSetIoRefs(val, transitiveIoRefs(name, env, ioNames)) : NIL);
+})(); }, envComponents(env)); };
+
+  // component-pure?
+  var componentPure_p = function(name, env, ioNames) { return isEmpty(transitiveIoRefs(name, env, ioNames)); };
+
 
   // =========================================================================
   // Platform interface — DOM adapter (browser-only)
@@ -3626,6 +3671,10 @@ callExpr.push(dictGet(kwargs, k)); } }
     componentsNeeded: componentsNeeded,
     pageComponentBundle: pageComponentBundle,
     pageCssClasses: pageCssClasses,
+    scanIoRefs: scanIoRefs,
+    transitiveIoRefs: transitiveIoRefs,
+    computeAllIoRefs: computeAllIoRefs,
+    componentPure_p: componentPure_p,
     _version: "ref-2.0 (boot+cssx+dom+engine+html+orchestration+parser+sx, bootstrap-compiled)"
   };
 
@@ -3649,4 +3698,4 @@ callExpr.push(dictGet(kwargs, k)); } }
   if (typeof module !== "undefined" && module.exports) module.exports = Sx;
   else global.Sx = Sx;
 
-})(typeof globalThis !== "undefined" ? globalThis : typeof window !== "undefined" ? window : this);
+})(typeof globalThis !== "undefined" ? globalThis : typeof window !== "undefined" ? window : this);