feat(sacred-valley): card factory, registry ordering, view skeleton

Adds the Plan 6 card framework: svCard() chrome factory, pure orderCards()
ordering helper with unit tests, three stub card modules (clock/weather/host-perf),
and rewrites sacred_valley.js with the two-band layout that mounts ordered cards.

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

public/views/cards/clock.js

@@ -0,0 +1,2 @@
+// temporary stub — filled in Task 5
+export default { id: 'clock', title: 'Clock', size: 's', mount() {}, start() {}, stop() {} };

public/views/cards/host_perf.js

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+// temporary stub — filled in Task 9
+export default { id: 'host-perf', title: 'Host Perf', size: 'm', mount() {}, start() {}, stop() {} };

public/views/cards/registry.js

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+// Pure ordering logic (kept DOM-free so it is unit-testable). The card MODULES
+// themselves are imported by sacred_valley.js, which passes their defs here.
+export function orderCards(defs, layout = { card_order: [], hidden: [] }) {
+  const byId = new Map(defs.map(d => [d.id, d]));
+  const hidden = new Set(layout.hidden || []);
+  const out = [];
+  for (const id of layout.card_order || []) {
+    if (byId.has(id) && !hidden.has(id)) { out.push(byId.get(id)); byId.delete(id); }
+  }
+  for (const d of defs) {
+    if (byId.has(d.id) && !hidden.has(d.id)) out.push(d);
+  }
+  return out;
+}

public/views/cards/weather.js

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+// temporary stub — filled in Task 7
+export default { id: 'weather', title: 'Weather', size: 's', mount() {}, start() {}, stop() {} };