Replace env free-variable threading with IO-primitive auto-fetch macros

Layout components now self-resolve context (cart-mini, auth-menu, nav-tree,
rights, URLs) via new IO primitives (root-header-ctx, select-colours,
account-nav-ctx, app-rights) and defmacro wrappers (~root-header-auto,
~auth-header-row-auto, ~root-mobile-auto). This eliminates _ctx_to_env(),
HELPER_CSS_CLASSES, and verbose :key threading across all 10 services.

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

shared/sx/primitives_io.py

@@ -45,6 +45,10 @@ IO_PRIMITIVES: frozenset[str] = frozenset({
     "abort",
     "url-for",
     "route-prefix",
+    "root-header-ctx",
+    "select-colours",
+    "account-nav-ctx",
+    "app-rights",
 })
 
 
@@ -378,6 +382,106 @@ async def _io_route_prefix(
     return route_prefix()
 
 
+async def _io_root_header_ctx(
+    args: list[Any], kwargs: dict[str, Any], ctx: RequestContext
+) -> dict[str, Any]:
+    """``(root-header-ctx)`` → dict with all root header values.
+
+    Fetches cart-mini, auth-menu, nav-tree fragments and computes
+    settings-url / is-admin from rights.  Result is cached on ``g``
+    per request so multiple calls (e.g. header + mobile) are free.
+    """
+    from quart import g, current_app, request
+    cached = getattr(g, "_root_header_ctx", None)
+    if cached is not None:
+        return cached
+
+    from shared.infrastructure.fragments import fetch_fragments
+    from shared.infrastructure.cart_identity import current_cart_identity
+    from shared.infrastructure.urls import app_url
+    from shared.config import config
+    from .types import NIL
+
+    user = getattr(g, "user", None)
+    ident = current_cart_identity()
+
+    cart_params: dict[str, Any] = {}
+    if ident["user_id"] is not None:
+        cart_params["user_id"] = ident["user_id"]
+    if ident["session_id"] is not None:
+        cart_params["session_id"] = ident["session_id"]
+
+    auth_params: dict[str, Any] = {}
+    if user and getattr(user, "email", None):
+        auth_params["email"] = user.email
+
+    nav_params = {"app_name": current_app.name, "path": request.path}
+
+    cart_mini, auth_menu, nav_tree = await fetch_fragments([
+        ("cart", "cart-mini", cart_params or None),
+        ("account", "auth-menu", auth_params or None),
+        ("blog", "nav-tree", nav_params),
+    ])
+
+    rights = getattr(g, "rights", None) or {}
+    is_admin = (
+        rights.get("admin", False)
+        if isinstance(rights, dict)
+        else getattr(rights, "admin", False)
+    )
+
+    result = {
+        "cart-mini": cart_mini or NIL,
+        "blog-url": app_url("blog", ""),
+        "site-title": config()["title"],
+        "app-label": current_app.name,
+        "nav-tree": nav_tree or NIL,
+        "auth-menu": auth_menu or NIL,
+        "nav-panel": NIL,
+        "settings-url": app_url("blog", "/settings/") if is_admin else "",
+        "is-admin": is_admin,
+    }
+    g._root_header_ctx = result
+    return result
+
+
+async def _io_select_colours(
+    args: list[Any], kwargs: dict[str, Any], ctx: RequestContext
+) -> str:
+    """``(select-colours)`` → the shared select/hover CSS class string."""
+    from quart import current_app
+    return current_app.jinja_env.globals.get("select_colours", "")
+
+
+async def _io_account_nav_ctx(
+    args: list[Any], kwargs: dict[str, Any], ctx: RequestContext
+) -> Any:
+    """``(account-nav-ctx)`` → account nav fragments as SxExpr, or NIL.
+
+    Reads ``g.account_nav`` (set by account service's before_request hook),
+    wrapping HTML strings in ``~rich-text`` for SX rendering.
+    """
+    from quart import g
+    from .types import NIL
+    from .parser import SxExpr
+    val = getattr(g, "account_nav", None)
+    if not val:
+        return NIL
+    if isinstance(val, SxExpr):
+        return val
+    # HTML string → wrap for SX rendering
+    escaped = str(val).replace("\\", "\\\\").replace('"', '\\"')
+    return SxExpr(f'(~rich-text :html "{escaped}")')
+
+
+async def _io_app_rights(
+    args: list[Any], kwargs: dict[str, Any], ctx: RequestContext
+) -> dict[str, Any]:
+    """``(app-rights)`` → user rights dict from ``g.rights``."""
+    from quart import g
+    return getattr(g, "rights", None) or {}
+
+
 _IO_HANDLERS: dict[str, Any] = {
     "frag": _io_frag,
     "query": _io_query,
@@ -394,4 +498,8 @@ _IO_HANDLERS: dict[str, Any] = {
     "abort": _io_abort,
     "url-for": _io_url_for,
     "route-prefix": _io_route_prefix,
+    "root-header-ctx": _io_root_header_ctx,
+    "select-colours": _io_select_colours,
+    "account-nav-ctx": _io_account_nav_ctx,
+    "app-rights": _io_app_rights,
 }