fix(8.0): close GA-blocking correctness gaps from the readiness audit

- Version-coupling cold-init: getBrainyVersion() returned a stale build-time
  default ('3.14.0') on the FIRST synchronous call — the one loadPlugins() makes
  to build context.version — because the package.json read was async. A native
  provider declaring a realistic `>=8.0.0` range was therefore rejected on cold
  init. version.ts now reads package.json synchronously (8.0 targets Node-like
  runtimes only); added a cold-init coupling regression with a `^8.0.0` plugin.
- No-silent-failures on the highest-fan-in read path: getNouns()/getVerbs()
  converted a storage read failure into a success-shaped empty page, which the
  cold-start rebuild then read as "store empty" and skipped the rebuild — booting
  a permanently-empty index with no signal (the same silent-failure class as the
  phantom bug). Both now re-throw a named BrainyError; the rebuild path re-throws
  read failures (fail loud) and records a queryable degraded state, surfaced via
  checkHealth(), for non-fatal rebuild hiccups.
- LSM SSTable leak: graph compaction wrote a merged SSTable but only dropped the
  old ones from the manifest, orphaning their payloads forever ("In production
  we'd add a cleanup mechanism"). Added StorageAdapter.deleteMetadata() and now
  reclaim each compacted-away SSTable.
- Documented the two headline methods add() and find() (the only undocumented
  public methods on the class).

Full gate green: build, unit 1512, integration 607.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/storage/adapters/baseStorageAdapter.ts

@@ -53,6 +53,8 @@ export abstract class BaseStorageAdapter implements StorageAdapter {
 
   abstract getMetadata(id: string): Promise<any | null>
 
+  abstract deleteMetadata(id: string): Promise<void>
+
   abstract getNounMetadata(id: string): Promise<any | null>
 
   abstract getVerbMetadata(id: string): Promise<any | null>