feat(8.0): version-coupling guard — a mismatched/failed native plugin fails loud, never silent JS fallback

A wrong or missing accelerator (@soulcraft/cor) used to silently degrade to the
default JS engine — the #1 source of invisible cross-repo drift. Brainy does no
plugin auto-detection (a registered plugin is always explicitly requested via
config.plugins or brain.use()), so any mismatch/failure is now fatal:

- BrainyPlugin gains optional `brainyRange` (semver range of brainy it supports);
  init() throws if the running brainy is outside it. New dep-free, prerelease-safe
  matcher pluginRangeSatisfies() (8.0.0-rc1 satisfies >=8.0.0).
- activateAll(): a plugin that THROWS during activate now re-throws (was swallowed
  to a JS fallback); a graceful decline (activate()→false) stays non-fatal but logs
  a loud warning.
- loadPlugins(): an explicitly-listed package that can't load — or isn't a valid
  plugin — throws (was a silent skip).
- Provider-key cliff: a pre-8.0 plugin that registers a legacy vector key
  ('hnsw'/'diskann') but not the 8.0 'vector' key throws (brainy 8.x reads only
  'vector', so it would otherwise run JS vectors invisibly).

Tests: tests/unit/plugin-version-coupling.test.ts (range matcher incl. rc1; range
mismatch / activate-throw / cliff / missing-package all throw; decline non-fatal).
Updated two plugin.test.ts cases that asserted the old silent-swallow behavior.
Build green; 1464 unit green. cor declares its brainyRange per handoff LV.1 #2.

tests/unit/plugin.test.ts

@@ -71,7 +71,7 @@ describe('PluginRegistry', () => {
     expect(registry.getActivePlugins()).toEqual([])
   })
 
-  it('should handle plugin that throws during activate', async () => {
+  it('throws (does not silently swallow) when a plugin throws during activate', async () => {
     const plugin: BrainyPlugin = {
       name: 'broken-plugin',
       activate: async () => {
@@ -85,9 +85,10 @@ describe('PluginRegistry', () => {
       version: '7.9.3'
     }
 
-    // Should not throw — graceful fallback
-    const activated = await registry.activateAll(context)
-    expect(activated).toEqual([])
+    // A registered plugin is always explicitly requested (config.plugins or
+    // brain.use(); brainy does no auto-detection), so a hard activation failure
+    // must surface — never a silent fall-back to the default engine.
+    await expect(registry.activateAll(context)).rejects.toThrow(/failed to activate|activation failed/)
     expect(registry.getActivePlugins()).toEqual([])
   })
 
@@ -279,7 +280,7 @@ describe('Brainy plugin integration', () => {
     await brain.close()
   })
 
-  it('should fall back gracefully when plugin throws', async () => {
+  it('throws (no silent fallback) when an explicitly-used plugin crashes on activate', async () => {
     const mockPlugin: BrainyPlugin = {
       name: 'crashing-plugin',
       activate: async () => {
@@ -293,18 +294,10 @@ describe('Brainy plugin integration', () => {
     })
     brain.use(mockPlugin)
 
-    // Should not throw — graceful fallback to TS
-    await brain.init()
-    expect(brain.getActivePlugins()).toEqual([])
-
-    const id = await brain.add({
-      data: { name: 'test' },
-      type: NounType.Concept,
-      metadata: { tag: 'unit-test' }
-    })
-    expect(id).toBeTypeOf('string')
-
-    await brain.close()
+    // A brain.use()'d plugin is explicitly requested — a hard activation crash
+    // must surface as a failed init(), NOT a silent degrade to the default
+    // engine (the version-coupling guard; see plugin-version-coupling.test.ts).
+    await expect(brain.init()).rejects.toThrow(/failed to activate|native module not found/)
   })
 
   it('should use() return this for chaining', () => {