feat: vector provider identity is a required name field (hnsw-js), rendered [vector-index:<name>]

Reconciles the vector-index rename to the ruled three-layer naming: the
provider contract's identity field is now a REQUIRED readonly name (was
optional providerId), self-reported and truthful, rendered as
[vector-index:<name>] where the index identifies itself and stamped into
the op-name strings journals already parse (AddToVectorIndex(<name>)).
The built-in JS engine names itself hnsw-js. A runtime provider instance
compiled against the previous optional contract is tolerated - never
crashed on, never silently mislabeled: it stamps unknown-provider and
emits one loud warning naming the missing field. Graph index operations
keep their static names (they never interpolate provider identity), and
no public API exports a provider-routed hnsw-carrying name, so no
deprecation shim is required.

src/hnsw/hnswIndex.ts

@@ -54,8 +54,8 @@ export class HnswFlushError extends Error {
  * acceleration provider).
  */
 export class JsHnswVectorIndex implements VectorIndexProvider {
-  /** Self-identifies as the built-in JS fallback engine — see {@link VectorIndexProvider.providerId}. */
-  readonly providerId = 'js-hnsw'
+  /** Self-identifies as the built-in JS fallback engine — see {@link VectorIndexProvider.name}. */
+  readonly name = 'hnsw-js'
 
   private nouns: Map<string, HNSWNoun> = new Map()
   /**