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

gsd-core/bin/lib/capability-registry.cjs

@@ -618,14 +618,6 @@ const capabilities = {
         "stateIO": "filesystem",
         "transport": "mcp",
         "runtime": "node"
-      },
-      "hostBehaviors": {
-        "reapplyCommand": "/gsd-update --reapply",
-        "frontmatterDialect": "cline",
-        "skipSharedHooksInstall": true,
-        "localTargetIsProjectRoot": true,
-        "clineRulesSurface": true,
-        "localCommandsViaRules": true
       }
     }
   },
@@ -1382,6 +1374,21 @@ const capabilities = {
       "writesSharedSettings": true,
       "permissionWriter": null,
       "extendedHookEvents": [],
+      "extensionEvents": "hermes",
+      "hostBehaviors": {
+        "skillFrontmatterVersion": true,
+        "skillsManifestPrefix": "skills/gsd/",
+        "trackCategoryDescription": true,
+        "writeCategoryDescription": true,
+        "reportSkillsCount": true,
+        "legacyCommandsGsdCleanup": true,
+        "brandingRewrites": {
+          "CLAUDE.md": "HERMES.md",
+          "Claude Code": "Hermes Agent",
+          ".claude/": ".hermes/"
+        },
+        "reapplyCommand": "gsd-update --reapply (mention the skill name)"
+      },
       "hostIntegration": {
         "embeddingMode": "imperative",
         "commandSurface": "slash-programmatic",
@@ -4037,14 +4044,6 @@ const runtimes = {
         "stateIO": "filesystem",
         "transport": "mcp",
         "runtime": "node"
-      },
-      "hostBehaviors": {
-        "reapplyCommand": "/gsd-update --reapply",
-        "frontmatterDialect": "cline",
-        "skipSharedHooksInstall": true,
-        "localTargetIsProjectRoot": true,
-        "clineRulesSurface": true,
-        "localCommandsViaRules": true
       }
     }
   },
@@ -4497,6 +4496,21 @@ const runtimes = {
       "writesSharedSettings": true,
       "permissionWriter": null,
       "extendedHookEvents": [],
+      "extensionEvents": "hermes",
+      "hostBehaviors": {
+        "skillFrontmatterVersion": true,
+        "skillsManifestPrefix": "skills/gsd/",
+        "trackCategoryDescription": true,
+        "writeCategoryDescription": true,
+        "reportSkillsCount": true,
+        "legacyCommandsGsdCleanup": true,
+        "brandingRewrites": {
+          "CLAUDE.md": "HERMES.md",
+          "Claude Code": "Hermes Agent",
+          ".claude/": ".hermes/"
+        },
+        "reapplyCommand": "gsd-update --reapply (mention the skill name)"
+      },
       "hostIntegration": {
         "embeddingMode": "imperative",
         "commandSurface": "slash-programmatic",

gsd-core/bin/lib/capability-validator.cjs

@@ -709,7 +709,7 @@ const VALID_HOOK_EVENTS = new Set(['claude', 'gemini']);
 // DISTINCT from hookEvents (managed-hook dialect): extensionEvents describes the
 // plugin-owned event subset imperative hosts expose (opencode / pi); 'none' = the
 // host exposes no extension surface (engine owns the bus, e.g. VS Code).
-const VALID_EXTENSION_EVENTS = new Set(['opencode', 'pi', 'none']);
+const VALID_EXTENSION_EVENTS = new Set(['opencode', 'pi', 'hermes', 'none']);
 const VALID_SANDBOX_TIERS = new Set(['none', 'codex-agent-sandbox']);
 const VALID_ARTIFACT_KIND_NAMES = new Set(['commands', 'agents', 'skills', 'kimi-agents']);
 const VALID_ARTIFACT_NESTINGS = new Set(['flat', 'nested']);