docs(website): record what the atlas spike proved

Part 7 of MODULE_API.md: the three exit criteria and their results, the two
contract changes the spike forced (ctx.express/ctx.validator and
window.__rg.jsxRuntime), the empirical confirmation of the OpenAPI split, the
loader's tested failure guarantees, and the three artifacts in the branch that
are consequences of stopping at six routes rather than intended shape.

Phase 1 is complete: docs/website/MODULE_API.md is written and the spike met
every exit criterion on website branch spike/module-atlas (cut from edge, never
merged).

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

website/MODULE_SYSTEM.md

@@ -392,6 +392,13 @@ hook. The spike must *also* prove the §2.6 chunk load end to end, since that is
 decision in the plan. Exit criteria: no internal-file imports, `npm run routes:manifest` produces a
 zero-line diff, and the chunk loads under the enforced CSP.
 
+**Phase 1 is complete.** The spike ran on `website` branch `spike/module-atlas` (cut from `edge`,
+never merged) and **met all three exit criteria** — see [`MODULE_API.md`](MODULE_API.md) Part 7. §2.6
+survives intact: the prebuilt chunk loads and renders under `script-src 'self'` with zero violation
+reports. The one thing it changed is that §2.6's one-React rule turns out to have a server-side twin
+nobody had written down — a module cannot resolve core's `express` either, so core hands that over
+too (API §7.2).
+
 **Phase 2 — Core scaffolding, no behaviour change.** One PR each, in order:
 
 1. `installed_modules` table + the §2.4 state machine.