Unify scoped effects: scope as general primitive, provide as sugar

- Add `scope` special form to eval.sx: (scope name body...) or
  (scope name :value v body...) — general dynamic scope primitive
- `provide` becomes sugar: (provide name value body...) calls scope
- Rename provide-push!/provide-pop! to scope-push!/scope-pop! throughout
  all adapters (async, dom, html, sx) and platform implementations
- Update boundary.sx: Tier 5 now "Scoped effects" with scope-push!/
  scope-pop! as primary, provide-push!/provide-pop! as aliases
- Add scope form handling to async adapter and aser wire format
- Update sx-browser.js, sx_ref.py (bootstrapped output)
- Add scopes.sx docs page, update provide/spreads/demo docs
- Update nav-data, page-functions, docs page definitions

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

shared/sx/ref/platform_js.py

@@ -883,8 +883,7 @@ PREAMBLE = '''\
   function SxSpread(attrs) { this.attrs = attrs || {}; }
   SxSpread.prototype._spread = true;
 
-  var _collectBuckets = {};
-  var _provideStacks = {};
+  var _scopeStacks = {};
 
   function isSym(x) { return x != null && x._sym === true; }
   function isKw(x) { return x != null && x._kw === true; }
@@ -1098,14 +1097,17 @@ PRIMITIVES_JS_MODULES: dict[str, str] = {
 ''',
 
     "stdlib.spread": '''
-  // stdlib.spread — spread + collect primitives
+  // stdlib.spread — spread + collect + scope primitives
   PRIMITIVES["make-spread"] = makeSpread;
   PRIMITIVES["spread?"] = isSpread;
   PRIMITIVES["spread-attrs"] = spreadAttrs;
   PRIMITIVES["collect!"] = sxCollect;
   PRIMITIVES["collected"] = sxCollected;
   PRIMITIVES["clear-collected!"] = sxClearCollected;
-  // provide/context/emit! — render-time dynamic scope
+  // scope — unified render-time dynamic scope
+  PRIMITIVES["scope-push!"] = scopePush;
+  PRIMITIVES["scope-pop!"] = scopePop;
+  // provide-push!/provide-pop! — aliases for scope-push!/scope-pop!
   PRIMITIVES["provide-push!"] = providePush;
   PRIMITIVES["provide-pop!"] = providePop;
   PRIMITIVES["context"] = sxContext;
@@ -1174,44 +1176,54 @@ PLATFORM_JS_PRE = '''
   function isSpread(x) { return x != null && x._spread === true; }
   function spreadAttrs(s) { return s && s._spread ? s.attrs : {}; }
 
-  function sxCollect(bucket, value) {
-    if (!_collectBuckets[bucket]) _collectBuckets[bucket] = [];
-    var items = _collectBuckets[bucket];
-    if (items.indexOf(value) === -1) items.push(value);
+  function scopePush(name, value) {
+    if (!_scopeStacks[name]) _scopeStacks[name] = [];
+    _scopeStacks[name].push({value: value !== undefined ? value : NIL, emitted: [], dedup: false});
   }
-  function sxCollected(bucket) {
-    return _collectBuckets[bucket] ? _collectBuckets[bucket].slice() : [];
-  }
-  function sxClearCollected(bucket) {
-    if (_collectBuckets[bucket]) _collectBuckets[bucket] = [];
+  function scopePop(name) {
+    if (_scopeStacks[name] && _scopeStacks[name].length) _scopeStacks[name].pop();
   }
+  // Aliases — provide-push!/provide-pop! map to scope-push!/scope-pop!
+  var providePush = scopePush;
+  var providePop = scopePop;
 
-  function providePush(name, value) {
-    if (!_provideStacks[name]) _provideStacks[name] = [];
-    _provideStacks[name].push({value: value !== undefined ? value : NIL, emitted: []});
-  }
-  function providePop(name) {
-    if (_provideStacks[name] && _provideStacks[name].length) _provideStacks[name].pop();
-  }
   function sxContext(name) {
-    if (_provideStacks[name] && _provideStacks[name].length) {
-      return _provideStacks[name][_provideStacks[name].length - 1].value;
+    if (_scopeStacks[name] && _scopeStacks[name].length) {
+      return _scopeStacks[name][_scopeStacks[name].length - 1].value;
     }
     if (arguments.length > 1) return arguments[1];
     throw new Error("No provider for: " + name);
   }
   function sxEmit(name, value) {
-    if (_provideStacks[name] && _provideStacks[name].length) {
-      _provideStacks[name][_provideStacks[name].length - 1].emitted.push(value);
+    if (_scopeStacks[name] && _scopeStacks[name].length) {
+      var entry = _scopeStacks[name][_scopeStacks[name].length - 1];
+      if (entry.dedup && entry.emitted.indexOf(value) !== -1) return NIL;
+      entry.emitted.push(value);
     }
     return NIL;
   }
   function sxEmitted(name) {
-    if (_provideStacks[name] && _provideStacks[name].length) {
-      return _provideStacks[name][_provideStacks[name].length - 1].emitted.slice();
+    if (_scopeStacks[name] && _scopeStacks[name].length) {
+      return _scopeStacks[name][_scopeStacks[name].length - 1].emitted.slice();
     }
     return [];
   }
+  function sxCollect(bucket, value) {
+    if (!_scopeStacks[bucket] || !_scopeStacks[bucket].length) {
+      if (!_scopeStacks[bucket]) _scopeStacks[bucket] = [];
+      _scopeStacks[bucket].push({value: NIL, emitted: [], dedup: true});
+    }
+    var entry = _scopeStacks[bucket][_scopeStacks[bucket].length - 1];
+    if (entry.emitted.indexOf(value) === -1) entry.emitted.push(value);
+  }
+  function sxCollected(bucket) {
+    return sxEmitted(bucket);
+  }
+  function sxClearCollected(bucket) {
+    if (_scopeStacks[bucket] && _scopeStacks[bucket].length) {
+      _scopeStacks[bucket][_scopeStacks[bucket].length - 1].emitted = [];
+    }
+  }
 
   function lambdaParams(f) { return f.params; }
   function lambdaBody(f) { return f.body; }
@@ -3244,6 +3256,8 @@ def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has
     api_lines.append('    collect: sxCollect,')
     api_lines.append('    collected: sxCollected,')
     api_lines.append('    clearCollected: sxClearCollected,')
+    api_lines.append('    scopePush: scopePush,')
+    api_lines.append('    scopePop: scopePop,')
     api_lines.append('    providePush: providePush,')
     api_lines.append('    providePop: providePop,')
     api_lines.append('    context: sxContext,')