docs: serve hyperframes.json / registry JSON schemas (#304)

The three /schema/*.json URLs baked into every Hyperframes project as
\$schema references were all 404ing on the live docs site — blocking
editor autocomplete and validation for hyperframes.json, registry.json,
and registry-item.json.

Adds docs/schema/ so Mintlify serves the three expected URLs:
- /schema/hyperframes.json       (new — authored from ProjectConfig)
- /schema/registry.json          (mirrored from packages/core/schemas/)
- /schema/registry-item.json     (mirrored from packages/core/schemas/)

The registry schemas stay authoritative in packages/core/schemas/ where
they're npm-exported for @hyperframes/core consumers. scripts/sync-schemas.ts
mirrors them into docs/schema/ and a new --check mode fails the Docs
workflow if the two drift, so the npm copy and the docs copy can't
diverge silently.

Validated against the factory-series-c-video config + a default config
generated by hyperframes init; negative cases (missing registry,
extra top-level keys, empty required strings) reject as expected.

scripts/sync-schemas.ts

@@ -0,0 +1,60 @@
+#!/usr/bin/env tsx
+/**
+ * Mirror JSON Schemas from `packages/core/schemas/` into `docs/schema/` so
+ * Mintlify serves them at `https://hyperframes.heygen.com/schema/*`. The core
+ * copies stay authoritative — they're exported from `@hyperframes/core` for
+ * npm consumers — and this script is the single contract that prevents the
+ * docs mirror from drifting.
+ *
+ * Usage:
+ *   bun run sync-schemas         # copy core → docs
+ *   bun run sync-schemas --check # exit non-zero if copies are stale (CI)
+ *
+ * `docs/schema/hyperframes.json` is authored directly in docs (no source in
+ * core) so it's skipped by this script.
+ */
+
+import { readFileSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+
+const ROOT = join(import.meta.dirname, "..");
+const SOURCE_DIR = join(ROOT, "packages/core/schemas");
+const TARGET_DIR = join(ROOT, "docs/schema");
+const MIRRORED = ["registry.json", "registry-item.json"];
+
+function main() {
+  const checkOnly = process.argv.includes("--check");
+  let drift = 0;
+
+  for (const name of MIRRORED) {
+    const source = readFileSync(join(SOURCE_DIR, name), "utf-8");
+    const targetPath = join(TARGET_DIR, name);
+    const target = (() => {
+      try {
+        return readFileSync(targetPath, "utf-8");
+      } catch {
+        return null;
+      }
+    })();
+
+    if (target === source) {
+      console.log(`  ✓ ${name} in sync`);
+      continue;
+    }
+
+    drift++;
+    if (checkOnly) {
+      console.error(`  ✗ ${name} out of sync (run \`bun run sync-schemas\` to fix)`);
+      continue;
+    }
+    writeFileSync(targetPath, source);
+    console.log(`  → ${name} updated`);
+  }
+
+  if (checkOnly && drift > 0) {
+    console.error(`\n${drift} schema${drift === 1 ? "" : "s"} drifted from source.`);
+    process.exit(1);
+  }
+}
+
+main();