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/weather.js

@@ -0,0 +1,2 @@
+// temporary stub — filled in Task 7
+export default { id: 'weather', title: 'Weather', size: 's', mount() {}, start() {}, stop() {} };