Migrate all apps to defpage declarative page routes

Replace Python GET page handlers with declarative defpage definitions in .sx
files across all 8 apps (sx docs, orders, account, market, cart, federation,
events, blog). Each app now has sxc/pages/ with setup functions, layout
registrations, page helpers, and .sx defpage declarations.

Core infrastructure: add g I/O primitive, PageDef support for auth/layout/
data/content/filter/aside/menu slots, post_author auth level, and custom
layout registration. Remove ~1400 lines of render_*_page/render_*_oob
boilerplate. Update all endpoint references in routes, sx_components, and
templates to defpage_* naming.

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

shared/sx/evaluator.py

@@ -33,7 +33,7 @@ from __future__ import annotations
 
 from typing import Any
 
-from .types import Component, HandlerDef, Keyword, Lambda, Macro, NIL, RelationDef, Symbol
+from .types import Component, HandlerDef, Keyword, Lambda, Macro, NIL, PageDef, RelationDef, Symbol
 from .primitives import _PRIMITIVES
 
 
@@ -635,6 +635,85 @@ def _sf_defrelation(expr: list, env: dict) -> RelationDef:
     return defn
 
 
+def _sf_defpage(expr: list, env: dict) -> PageDef:
+    """``(defpage name :path "/..." :auth :public :content expr ...)``
+
+    Parses keyword args from the expression. All slot values are stored
+    as unevaluated AST — they are resolved at request time by execute_page().
+    """
+    if len(expr) < 2:
+        raise EvalError("defpage requires a name")
+    name_sym = expr[1]
+    if not isinstance(name_sym, Symbol):
+        raise EvalError(f"defpage name must be symbol, got {type(name_sym).__name__}")
+
+    # Parse keyword args — values are NOT evaluated (stored as AST)
+    slots: dict[str, Any] = {}
+    i = 2
+    while i < len(expr):
+        key = expr[i]
+        if isinstance(key, Keyword) and i + 1 < len(expr):
+            slots[key.name] = expr[i + 1]
+            i += 2
+        else:
+            i += 1
+
+    # Required fields
+    path = slots.get("path")
+    if path is None:
+        raise EvalError(f"defpage {name_sym.name} missing required :path")
+    if not isinstance(path, str):
+        raise EvalError(f"defpage {name_sym.name} :path must be a string")
+
+    auth_val = slots.get("auth", "public")
+    if isinstance(auth_val, Keyword):
+        auth: str | list = auth_val.name
+    elif isinstance(auth_val, list):
+        # (:rights "a" "b") → ["rights", "a", "b"]
+        auth = []
+        for item in auth_val:
+            if isinstance(item, Keyword):
+                auth.append(item.name)
+            elif isinstance(item, str):
+                auth.append(item)
+            else:
+                auth.append(_eval(item, env))
+    else:
+        auth = str(auth_val) if auth_val else "public"
+
+    # Layout — keep unevaluated
+    layout = slots.get("layout")
+    if isinstance(layout, Keyword):
+        layout = layout.name
+    elif isinstance(layout, list):
+        # Keep as unevaluated list for execute_page to resolve at request time
+        pass
+
+    # Cache — evaluate if present (it's a static config dict)
+    cache_val = slots.get("cache")
+    cache = None
+    if cache_val is not None:
+        cache_result = _eval(cache_val, env)
+        if isinstance(cache_result, dict):
+            cache = cache_result
+
+    page = PageDef(
+        name=name_sym.name,
+        path=path,
+        auth=auth,
+        layout=layout,
+        cache=cache,
+        data_expr=slots.get("data"),
+        content_expr=slots.get("content"),
+        filter_expr=slots.get("filter"),
+        aside_expr=slots.get("aside"),
+        menu_expr=slots.get("menu"),
+        closure=dict(env),
+    )
+    env[f"page:{name_sym.name}"] = page
+    return page
+
+
 _SPECIAL_FORMS: dict[str, Any] = {
     "if": _sf_if,
     "when": _sf_when,
@@ -657,6 +736,7 @@ _SPECIAL_FORMS: dict[str, Any] = {
     "defmacro": _sf_defmacro,
     "quasiquote": _sf_quasiquote,
     "defhandler": _sf_defhandler,
+    "defpage": _sf_defpage,
 }