fix: user metadata named 'level' is a real field everywhere — the engine-internal node layer no longer shadows it in sort/filter/aggregation, and the indexing views stop stamping a phantom 0 into its column; index epoch 2 rebuilds existing brains at first open

Also completes the v8.10.2 write-granularity law for the transact() plan
path: a metadata-only batch update never rewrites the vector-bearing noun
record (planUpdate staged the unconditional save the update() fix removed).
Seven pins in tests/integration/level-field-shadow.test.ts including the
reporting consumer's exact repro rows; orderBy JSDoc documents the ordering
contract and the announced field-addressing law.

tests/integration/orderby-sort-bug.test.ts

@@ -215,7 +215,6 @@ describe('resolveEntityField helper', () => {
       'id',
       'vector',
       'connections',
-      'level',
       'type',
       'confidence',
       'weight',
@@ -228,5 +227,9 @@ describe('resolveEntityField helper', () => {
     for (const field of expected) {
       expect(STANDARD_ENTITY_FIELDS.has(field)).toBe(true)
     }
+    // `level` is deliberately NOT resolvable: it is HNSW plumbing, and listing
+    // it here shadowed user metadata named `level` in every by-name read
+    // (the reserved-name shadow bug). Plumbing stays out of the resolver.
+    expect(STANDARD_ENTITY_FIELDS.has('level')).toBe(false)
   })
 })