Exact asger toggle (theme key + prefers-color-scheme), responsive container + full site-chrome components

- weirsoe-theme.js: match asger.weirsoe.dk exactly — localStorage['theme'],
  prefers-color-scheme default, light<->dark click delegation.
- Container tokens + .wt-container(/--wide/--narrow/--bleed); Bulma adapter
  constrains content to a centred column past tablet (full-bleed on phones).
- Site chrome extracted from agw/pw so it can drop its hardcoded CSS: .wt-header
  /.wt-nav/.wt-brand/.wt-nav-link/.wt-main/.wt-footer, postcard .wt-card(+date/
  title/desc, --raised) and .wt-chip. README components table + theme-color note.

adapters/bulma.css

@@ -101,3 +101,11 @@ hr { background-color: var(--color-border); }
 /* Misc */
 details summary { color: var(--color-accent); }
 .section { padding-top: 2rem; }
+
+/* Responsive content width: full-bleed on phones, a centred readable column on
+   large screens (so a wishlist doesn't stretch edge-to-edge on a desktop). The
+   app marks a wrapper with .container.fullwidth; constrain it past tablet. */
+@media (min-width: 769px) {
+  .container.fullwidth { max-width: 52rem; margin-left: auto; margin-right: auto; }
+  .container.fullwidth.is-wide { max-width: 72rem; }
+}