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).

tests/unit/plugin-activation-loudness.test.ts

@@ -0,0 +1,71 @@
+/**
+ * @module tests/unit/plugin-activation-loudness
+ * @description The plugin-activation swallow closes. Two laws:
+ * (1) THE NOT-INSTALLED FREE PASS IS EXACT — a resolution failure earns the
+ *     silent skip ONLY when it names the probed package itself, terminated
+ *     where the name ends. A missing platform-binary SIBLING package
+ *     ("<pkg>-linux-x64-gnu" — what a deploy replacing node_modules
+ *     mid-restart leaves), an inner file path, or a dependency failure is a
+ *     BROKEN install and must fail loud. A production storm ran 90s of
+ *     throttled WASM behind this exact prefix-match hole.
+ * (2) A GRACEFUL DECLINE IS NARRATED ON THE ALWAYS-ON CHANNEL — activate()
+ *     returning false warns via prodLog, which `silent: true` cannot patch
+ *     away; a declined accelerator is never an invisible degrade.
+ */
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { Brainy } from '../../src/brainy.js'
+import { prodLog } from '../../src/utils/logger.js'
+
+const isNotInstalled = (error: unknown, pkg: string): boolean =>
+  (Brainy as unknown as {
+    isPackageNotInstalledError(e: unknown, p: string): boolean
+  }).isPackageNotInstalledError(error, pkg)
+
+const resolutionError = (message: string): Error => {
+  const e = new Error(message) as Error & { code?: string }
+  e.code = 'ERR_MODULE_NOT_FOUND'
+  return e
+}
+
+describe('the not-installed free pass is exact', () => {
+  const PKG = '@soulcraft/cor'
+
+  it('the package itself, quoted or bare → not-installed (the one free path)', () => {
+    expect(isNotInstalled(resolutionError(`Cannot find package '${PKG}' imported from /app/x.js`), PKG)).toBe(true)
+    expect(isNotInstalled(resolutionError(`Cannot find module ${PKG}`), PKG)).toBe(true)
+  })
+
+  it('a missing platform-binary SIBLING package is a broken install, never not-installed', () => {
+    expect(isNotInstalled(resolutionError(`Cannot find package '${PKG}-linux-x64-gnu' imported from /app`), PKG)).toBe(false)
+    expect(isNotInstalled(resolutionError(`Failed to resolve ${PKG}-darwin-arm64`), PKG)).toBe(false)
+  })
+
+  it('an inner file path or a non-resolution error is never not-installed', () => {
+    expect(isNotInstalled(resolutionError(`Cannot find module '/app/node_modules/${PKG}/native/b.node'`), PKG)).toBe(false)
+    expect(isNotInstalled(new Error(`dlopen failed: wrong ELF class in ${PKG}`), PKG)).toBe(false)
+  })
+})
+
+describe('a graceful decline is narrated on the always-on channel', () => {
+  afterEach(() => vi.restoreAllMocks())
+
+  it('activate() → false warns via prodLog even under silent: true', async () => {
+    process.env.BRAINY_DETERMINISTIC_EMBEDDINGS = 'true'
+    const warn = vi.spyOn(prodLog, 'warn')
+    const brain: any = new Brainy({
+      requireSubtype: false,
+      storage: { type: 'memory' },
+      silent: true,
+      dimensions: 384
+    })
+    brain.use({ name: 'declining-accelerator', activate: async () => false })
+    await brain.init()
+    try {
+      expect(
+        warn.mock.calls.some((c) => String(c[0]).includes('"declining-accelerator" declined activation'))
+      ).toBe(true)
+    } finally {
+      await brain.close().catch(() => {})
+    }
+  })
+})