chore: rename to @soulcraftlabs/brainy for Open Brainy on The Source

Prepares the repo for its new home at soulcraftlabs/open-brainy ahead
of the Forgejo transfer: package name, publish registry, release
script, and every install/import reference across docs, src, tests,
examples, and integrations now point at @soulcraftlabs/brainy on
The Source. The npmjs storefront leg and byte-identity pair
verification are stripped from the release script — The Source is
now the only publish target. README gains an Open Brainy explainer
and a registry note for consumers.

@soulcraft/brainy 10.4.2 was the last release under the old name.

tests/unit/brainy/migration-deference.test.ts

@@ -15,7 +15,7 @@
  * - Hook 2: the public `brain.stampBrainFormat()` the provider calls once its
  *   background migration has verified-and-swapped, authoring the shared
  *   `_system/brain-format.json` marker.
- * - Hook 3: the marker module is re-exported at `@soulcraft/brainy/brain-format`
+ * - Hook 3: the marker module is re-exported at `@soulcraftlabs/brainy/brain-format`
  *   so cor reads the SAME `EXPECTED_INDEX_EPOCH` / `CURRENT_DATA_FORMAT` constants
  *   (single source of truth, no duplicated value).
  *
@@ -242,7 +242,7 @@ describe('rc.8 no-freeze migration deference (isMigrating / stampBrainFormat / b
   // --- Hook 3: marker module export ----------------------------------------
 
   it('the brain-format marker module exports the compiled epoch + data-format constants', () => {
-    // cor imports these from '@soulcraft/brainy/brain-format' (Hook 3) so both
+    // cor imports these from '@soulcraftlabs/brainy/brain-format' (Hook 3) so both
     // sides share ONE source of truth — no duplicated constant to drift.
     // Epoch 3: the namespace-law key split (bare user keys · literal
     // 'system.<field>' scalars, 2026-08-03) — every brain rebuilds onto the