{% comment %} Board | Chat page switcher — rendered on BOTH top-level pages so neither one is reachable only by typing its URL. Operator, 2026-07-28 (TG): 「http://127.0.0.1:8051/chat/ 今だと chat が隠し URL みたいになってしまっているので、ホームに Board | Chat のスイッチャーを付けて欲しいです。」 They are migrating off Telegram onto this chat, so an undiscoverable chat page is a migration blocker, not a polish item. MOUNT AWARENESS — read before touching an href here. The hub mounts this app under a sub-path (e.g. /apps/cards/), where a hardcoded "/" lands on the hub's own landing page and a hardcoded "/chat" 404s. Both prior bugs of this class (#556, #557) were exactly that. Every href is therefore built from `api_base` — the include root each view derives from `request.path` — which is the SAME mechanism board_v3.html's `API_BASE` const and chat.html's `` already use, and it is always "…/"-terminated. `{% templatetag openblock %} url {% templatetag closeblock %}` is deliberately NOT used: this urlconf is served both as its own ROOT_URLCONF (standalone `scitex-cards board`, where the `app_name` application namespace is never registered) and via `include()` on the hub — one reverse() spelling cannot serve both, whereas `api_base` is correct in either. Callers pass the page they are on: {% templatetag openblock %} include "scitex_cards/_page_switcher.html" with active="board" {% templatetag closeblock %} `api_base` is inherited from the page context — both views already provide it. Styling lives in static/scitex_cards/page-switcher.css; each host page feeds its own palette into that component's `--sw-*` tokens. {% endcomment %}