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.

docs/concepts/index-health.md

@@ -95,7 +95,7 @@ catchable error naming the reason:
 | `MetadataIndexNotReadyError` | `find({ where })` | The metadata/field index isn't serving — a filtered read would otherwise return `[]` indistinguishable from "no matches" |
 | `VectorIndexNotReadyError` | `find({ query })`, `similar()` | The vector index isn't serving — a semantic search would otherwise return `[]` indistinguishable from "nothing similar" |
 
-All three are exported from `@soulcraft/brainy`. Catch them where your application
+All three are exported from `@soulcraftlabs/brainy`. Catch them where your application
 needs to distinguish "this index isn't ready yet" from "there's genuinely nothing
 here" — a health dashboard, a retry policy, an operator alert. The fix is always
 the same: reconcile the index, either by reopening the brain (which brings every