fix(find): near() searches around the anchor's own vector, and refuses by name without one

The proximity search fetched its anchor through get(), which omits vectors
by default, then handed a zero-length vector to the index — every
find({ near }) refused with a dimension mismatch, for every caller. Found
by the Rust planner's first-contact pins comparing outcomes with and
without the planner on a refused shape. The anchor is now fetched with its
vector, and an anchor that has none refuses by name — a proximity search
around an unvectored row has no meaning and must not fail inside the index.
Pinned in tests/integration/find-near.test.ts.

src/brainy.ts

@@ -15892,8 +15892,18 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       )
     }
 
-    const nearEntity = await this.get(params.near.id)
+    // The anchor's VECTOR is the query; get() omits vectors by default, which
+    // fed a zero-length vector to the index and refused every near() with a
+    // dimension mismatch. Ask for it, and refuse by name when the anchor has
+    // none — a proximity search around an unvectored row has no meaning.
+    const nearEntity = await this.get(params.near.id, { includeVectors: true })
     if (!nearEntity) return []
+    if (!nearEntity.vector || nearEntity.vector.length === 0) {
+      throw new Error(
+        `find({ near }): entity '${params.near.id}' has no vector to search around — ` +
+          `it was never embedded (or was unvectored). Embed it, or search with a query instead.`
+      )
+    }
 
     const nearResults: [string, number][] = await this.index.search(nearEntity.vector, params.limit || 10)