Ban SafeText-as-child: only Safe nodes render unescaped

Tightens the child model so the type is honest end to end. Previously a
``SafeText``/``mark_safe`` string passed as a child rendered unescaped — a
trusted-HTML-as-string backdoor that ``Child = Node | str`` couldn't express
(every ``SafeText`` is a ``str``). Now ``_child_key`` escapes *every* string
child; the only way to put trusted pre-rendered HTML into the tree is a
``Safe`` node. So a ``str`` child is always untrusted text — which is exactly
what the renderer escapes.

Converted the trusted-HTML children that relied on the old passthrough:

- ``CsrfInput`` and the Alpine selectors (``GameStatusSelector`` /
  ``SessionDeviceSelector``) now return ``Safe`` nodes instead of ``mark_safe``
  strings — they are always tree children.
- ``popover_content`` is now a ``Child`` (it is rendered as a child); the one
  HTML caller (``LinkedPurchase``) passes ``Safe(...)``.
- View-side children that were ``mark_safe`` strings → ``Safe(...)``:
  ``_played_row`` (game detail), the stat SVGs and `` `` spacer (game),
  the login table (auth), the manual session-form field/label markup
  (session), and ``_purchase_name`` (stats).
- ``SimpleTable.header_action`` typed ``Child``.

The script-tag string helpers (``ModuleScript`` / ``StaticScript`` /
``ExternalScript``) stay ``SafeText`` strings: they are only ever joined into
the ``scripts=`` string, never used as tree children.

``Children`` regains a bare ``Node`` member (a single node child is valid);
the one ``*children`` site (``Popover``) normalises via ``as_children`` first.
Tests that asserted the old SafeText-passthrough now assert the new rule
(mark_safe child escaped; ``Safe`` node passes through). Full suite green
(445; +2 new escaping tests).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

games/views/stats_content.py

@@ -9,9 +9,18 @@ from django.template.defaultfilters import date as date_filter
 from django.template.defaultfilters import floatformat
 from django.urls import reverse
 from django.utils.html import conditional_escape
-from django.utils.safestring import mark_safe
-
-from common.components import A, Div, Element, GameLink, Node, Td, Th, Tr, YearPicker
+from common.components import (
+    A,
+    Div,
+    Element,
+    GameLink,
+    Node,
+    Safe,
+    Td,
+    Th,
+    Tr,
+    YearPicker,
+)
 from common.time import durationformat, format_duration
 
 _CELL = "px-2 sm:px-4 md:px-6 md:py-2"
@@ -70,7 +79,7 @@ def _purchase_name(purchase) -> Node:
         name = game_name or purchase.name
         link = GameLink(first_game.id, name)
         suffix = f" ({first_game.name} {purchase.get_type_display()})"
-        return mark_safe(str(link) + conditional_escape(suffix))
+        return Safe(str(link) + conditional_escape(suffix))
     name = game_name or first_game.name
     return GameLink(first_game.id, name)