fix(plugins): the silent-degrade doors close — a broken accelerator install can never read as absent

The auto-detection "not installed" heuristic accepted any resolution failure
whose message merely CONTAINED the package name, unterminated — so a missing
platform-binary sibling package (what a deploy replacing node_modules
mid-restart leaves behind) read as "the accelerator is not installed", and
brainy silently served the default WASM engines with zero journal lines. A
production restart storm paid 90 seconds of throttled WASM compile behind
exactly that hole. The name must now terminate where it ends (quote,
whitespace, punctuation, end) — a sibling package, an inner file path, or a
dependency failure is a broken install and init() throws, as the guard's own
law always stated.

Second door: activate() returning false (the documented graceful decline)
warned on console.warn, which `silent: true` patches away — an invisible
degrade. The decline now narrates via the always-on channel.

Also exports CanonicalCounts from the public surface (the coverage-ledger
denominator type consumers read through getCanonicalCounts()).

Pinned in tests/unit/plugin-activation-loudness.test.ts (five error shapes;
the decline warn under silent: true).

src/index.ts

@@ -389,7 +389,10 @@ import type {
   HNSWVerb,
   HNSWConfig,
   StorageAdapter,
-  DerivedFamilyDeclaration
+  DerivedFamilyDeclaration,
+  // The canonical count ledger a storage adapter maintains (counted + ALL-visibility
+  // scalars per family, the coverage-ledger denominators) — see StorageAdapter.getCanonicalCounts.
+  CanonicalCounts
 } from './coreTypes.js'
 
 // Export vector index implementation (the JS HNSW path)