Add macros, declarative handlers (defhandler), and convert all fragment routes to sx

Phase 1 — Macros: defmacro + quasiquote syntax (`, ,, ,@) in parser,
evaluator, HTML renderer, and JS mirror. Macro type, expansion, and
round-trip serialization.

Phase 2 — Expanded primitives: app-url, url-for, asset-url, config,
format-date, parse-int (pure); service, request-arg, request-path,
nav-tree, get-children (I/O); jinja-global, relations-from (pure).
Updated _io_service to accept (service "registry-name" "method" :kwargs)
with auto kebab→snake conversion. DTO-to-dict now expands datetime fields
into year/month/day convenience keys. Tuple returns converted to lists.

Phase 3 — Declarative handlers: HandlerDef type, defhandler special form,
handler registry (service → name → HandlerDef), async evaluator+renderer
(async_eval.py) that awaits I/O primitives inline within control flow.
Handler loading from .sx files, execute_handler, blueprint factory.

Phase 4 — Convert all fragment routes: 13 Python fragment handlers across
8 services replaced with declarative .sx handler files. All routes.py
simplified to uniform sx dispatch pattern. Two Jinja HTML handlers
(events/container-cards, events/account-page) kept as Python.

New files: shared/sx/async_eval.py, shared/sx/handlers.py,
shared/sx/tests/test_handlers.py, plus 13 handler .sx files under
{service}/sx/handlers/. MarketService.product_by_slug() added.

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

orders/bp/fragments/routes.py

@@ -1,29 +1,23 @@
 """Orders app fragment endpoints.
 
-Fragments:
-  account-nav-item   "orders" link for account dashboard
+Exposes sx fragments at ``/internal/fragments/<type>`` for consumption
+by other coop apps via the fragment client.
+
+All handlers are defined declaratively in .sx files under
+``orders/sx/handlers/`` and dispatched via the sx handler registry.
 """
+
 from __future__ import annotations
 
 from quart import Blueprint, Response, request
+
 from shared.infrastructure.fragments import FRAGMENT_HEADER
+from shared.sx.handlers import get_handler, execute_handler
 
 
 def register():
     bp = Blueprint("fragments", __name__, url_prefix="/internal/fragments")
 
-    async def _account_nav_item():
-        from shared.infrastructure.urls import orders_url
-        from shared.sx.helpers import sx_call
-
-        return sx_call("account-nav-item",
-                         href=orders_url("/"),
-                         label="orders")
-
-    _handlers = {
-        "account-nav-item": _account_nav_item,
-    }
-
     @bp.before_request
     async def _require_fragment_header():
         if not request.headers.get(FRAGMENT_HEADER):
@@ -31,10 +25,12 @@ def register():
 
     @bp.get("/<fragment_type>")
     async def get_fragment(fragment_type: str):
-        handler = _handlers.get(fragment_type)
-        if handler is None:
-            return Response("", status=200, content_type="text/sx")
-        src = await handler()
-        return Response(src, status=200, content_type="text/sx")
+        handler_def = get_handler("orders", fragment_type)
+        if handler_def is not None:
+            result = await execute_handler(
+                handler_def, "orders", args=dict(request.args),
+            )
+            return Response(result, status=200, content_type="text/sx")
+        return Response("", status=200, content_type="text/sx")
 
     return bp

orders/sx/handlers/account-nav-item.sx

@@ -0,0 +1,8 @@
+;; Orders account-nav-item fragment handler
+;;
+;; Renders the "orders" link for the account dashboard nav.
+
+(defhandler account-nav-item (&key)
+  (~account-nav-item
+    :href (app-url "orders" "/")
+    :label "orders"))

orders/sx/sx_components.py

@@ -19,8 +19,9 @@ from shared.sx.helpers import (
 )
 from shared.infrastructure.urls import market_product_url, cart_url
 
-# Load orders-specific .sx components at import time
-load_service_components(os.path.dirname(os.path.dirname(__file__)))
+# Load orders-specific .sx components + handlers at import time
+load_service_components(os.path.dirname(os.path.dirname(__file__)),
+                        service_name="orders")
 
 
 # ---------------------------------------------------------------------------