feat(#2091): migrate hermes onto EoS imperative adapter + extensionEvents dialect (ADR-1239)

- Fold 7 hardcoded isHermes/runtime === 'hermes' branches in bin/install.js into
  descriptor-driven _hostBehaviors lookups (skillFrontmatterVersion,
  skillsManifestPrefix, trackCategoryDescription, writeCategoryDescription,
  reportSkillsCount, legacyCommandsGsdCleanup, brandingRewrites)
- Add runtime.hostBehaviors block to capabilities/hermes/capability.json
- Register EXTENSION_EVENT_SURFACES.hermes (13 real plugin hook events) in
  src/host-integration.cts — replaces the borrowed hookEvents:'claude' 6-event
  surface that silently never fired on Hermes
- Add extensionEvents:'hermes' to the descriptor
- Add 'hermes' to VALID_EXTENSION_EVENTS in capability-validator.cjs
- Regenerate capability-registry.cjs
- Tests: hermes-imperative-reference (negotiation, axes, fail-closed, source-guard),
  hermes-dispatch-upgrade (dispatch posture, degradation, fail-closed)
- Changeset + docs update

src/host-integration.cts

@@ -559,6 +559,19 @@ const EXTENSION_EVENT_SURFACES: Readonly<Record<string, readonly string[]>> = Ob
     // permission decisions + session error surface.
     'permission.asked', 'permission.replied', 'session.error',
   ]),
+  // #2091 — Hermes Agent real plugin hook vocabulary (13 events).
+  // Cite: https://github.com/nousresearch/hermes-agent/blob/main/website/docs/user-guide/features/hooks.md
+  // Replaces the borrowed `hookEvents: "claude"` 6-event surface that silently
+  // never fired on Hermes.
+  hermes: Object.freeze([
+    'pre_tool_call', 'post_tool_call',
+    'pre_llm_call', 'post_llm_call',
+    'on_session_start', 'on_session_end',
+    'on_session_finalize', 'on_session_reset',
+    'subagent_start', 'subagent_stop',
+    'pre_gateway_dispatch', 'pre_approval_request',
+    'transform_tool_result',
+  ]),
   pi: Object.freeze(['tool_call']),
   none: Object.freeze([]),
 });