docs(nav): group Protocol Reference modules and clarify top-level nav

The docs site rendered fine but its information architecture was hard to
navigate: 238 of 366 pages live under Protocol Reference, and each module
was a single flat alphabetical list (system: 40, api: 38, kernel: 32, …).
The top-level "Protocol" (5 pages) vs "Protocol Reference" (238 pages)
split was also ambiguous.

Navigation-only changes (no content edits, no file moves):
- Add second-level `---section---` groups to the 8 largest reference
  modules (system, api, kernel, data, ui, cloud, automation, ai), turning
  each flat list into labeled logical groups. Smaller modules (≤9 pages)
  stay flat to avoid over-fragmenting short lists.
- Rename top-level "Protocol" → "Protocol Overview" to distinguish the
  conceptual intro from the per-module "Protocol Reference".
- Remove the empty, orphaned references/contracts/ folder.

Every regrouped meta.json was validated: valid JSON, every existing .mdx
covered, no dangling entries. Verified in the browser (grouped section
headers render correctly, no build errors).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: os-zhuang

content/docs/protocol/meta.json

@@ -1,4 +1,4 @@
 {
-  "title": "Protocol",
+  "title": "Protocol Overview",
   "pages": ["index", "objectql", "objectui", "objectos", "knowledge"]
 }

content/docs/references/ai/meta.json

@@ -1,16 +1,19 @@
 {
   "title": "AI Protocol",
   "pages": [
+    "---Agents & Tools---",
     "agent",
+    "tool",
+    "skill",
     "conversation",
-    "embedding",
-    "knowledge-document",
-    "knowledge-source",
     "mcp",
+    "---Knowledge & Embeddings---",
+    "knowledge-source",
+    "knowledge-document",
+    "embedding",
+    "---Models & Solutions---",
     "model-registry",
-    "skill",
     "solution-blueprint",
-    "tool",
     "usage"
   ]
-}
+}

content/docs/references/api/meta.json

@@ -1,43 +1,50 @@
 {
   "title": "API Protocol",
   "pages": [
-    "analytics",
-    "auth",
-    "auth-endpoints",
-    "automation-api",
-    "batch",
-    "connector",
-    "contract",
+    "---Overview---",
+    "protocol",
     "core-services",
-    "discovery",
-    "dispatcher",
     "documentation",
+    "discovery",
+    "---REST & HTTP---",
+    "rest-server",
+    "router",
     "endpoint",
-    "errors",
-    "events",
+    "object",
+    "batch",
     "export",
-    "feed-api",
-    "graphql",
     "http",
     "http-cache",
-    "identity",
+    "errors",
+    "versioning",
+    "---Query Interfaces---",
+    "query-adapter",
+    "graphql",
+    "odata",
+    "analytics",
     "metadata",
     "metadata-plugin",
+    "contract",
+    "---Auth & Identity---",
+    "auth",
+    "auth-endpoints",
+    "identity",
+    "---Realtime & Events---",
+    "realtime",
+    "realtime-shared",
+    "websocket",
+    "events",
+    "dispatcher",
     "notification",
-    "object",
-    "odata",
+    "feed-api",
+    "---Automation & Integration---",
+    "automation-api",
+    "connector",
+    "plugin-rest-api",
+    "---Packages & Storage---",
     "package-api",
     "package-registry",
-    "plugin-rest-api",
-    "protocol",
-    "query-adapter",
-    "realtime",
-    "realtime-shared",
     "registry",
-    "rest-server",
-    "router",
-    "storage",
-    "versioning",
-    "websocket"
+    "storage"
   ]
-}
+}

content/docs/references/automation/meta.json

@@ -1,18 +1,21 @@
 {
   "title": "Automation Protocol",
   "pages": [
-    "approval",
-    "bpmn-interop",
-    "connector",
-    "etl",
-    "execution",
+    "---Flows & Execution---",
     "flow",
-    "job",
+    "execution",
     "node-executor",
-    "offline",
     "state-machine",
-    "sync",
+    "bpmn-interop",
+    "---Triggers & Jobs---",
     "trigger-registry",
-    "webhook"
+    "job",
+    "webhook",
+    "offline",
+    "---Workflows & Integration---",
+    "approval",
+    "etl",
+    "sync",
+    "connector"
   ]
-}
+}

content/docs/references/cloud/meta.json

@@ -1,18 +1,21 @@
 {
   "title": "Cloud Protocol",
   "pages": [
-    "app-store",
-    "developer-portal",
+    "---Environments---",
     "environment",
     "environment-artifact",
     "environment-package",
+    "provisioning",
+    "tenant",
+    "---Marketplace & Distribution---",
     "marketplace",
     "marketplace-admin",
+    "app-store",
+    "developer-portal",
+    "---Packages---",
     "package",
     "package-version",
-    "plugin-security",
-    "provisioning",
     "template-manifest",
-    "tenant"
+    "plugin-security"
   ]
-}
+}

content/docs/references/contracts/meta.json

@@ -1,29 +1,35 @@
 {
   "title": "Data Protocol",
   "pages": [
+    "---Core Modeling---",
+    "object",
+    "field",
+    "validation",
+    "mapping",
+    "document",
+    "---Query & Filter---",
+    "query",
+    "filter",
+    "date-macros",
     "analytics",
+    "---Engine & Drivers---",
     "data-engine",
     "datasource",
-    "date-macros",
-    "document",
     "driver",
-    "driver-nosql",
     "driver-sql",
-    "external-catalog",
-    "external-lookup",
-    "feed",
-    "field",
-    "filter",
+    "driver-nosql",
+    "---Hooks & Lifecycle---",
     "hook",
     "hook-body",
-    "mapping",
+    "subscription",
+    "feed",
     "notification",
-    "object",
-    "query",
+    "---External Data---",
+    "external-catalog",
+    "external-lookup",
     "search-engine",
+    "---Seeding---",
     "seed",
-    "seed-loader",
-    "subscription",
-    "validation"
+    "seed-loader"
   ]
-}
+}

content/docs/references/data/meta.json

@@ -1,37 +1,42 @@
 {
   "title": "Kernel Protocol",
   "pages": [
-    "cli-extension",
-    "cluster",
+    "---Core Runtime---",
     "context",
-    "dependency-resolution",
-    "dev-plugin",
     "execution-context",
-    "feature",
     "manifest",
-    "metadata-customization",
-    "metadata-loader",
-    "metadata-persistence",
-    "metadata-plugin",
-    "metadata-protection",
+    "feature",
+    "service-registry",
+    "startup-orchestrator",
+    "cluster",
+    "state-machine",
+    "cli-extension",
+    "dev-plugin",
     "misc",
-    "package-artifact",
-    "package-registry",
-    "package-upgrade",
+    "---Plugin Lifecycle---",
     "plugin",
-    "plugin-capability",
-    "plugin-lifecycle-advanced",
-    "plugin-lifecycle-events",
+    "plugin-structure",
     "plugin-loading",
-    "plugin-registry",
+    "plugin-lifecycle-events",
+    "plugin-lifecycle-advanced",
     "plugin-runtime",
+    "plugin-registry",
+    "plugin-capability",
+    "---Plugin Security & Validation---",
     "plugin-security",
     "plugin-security-advanced",
-    "plugin-structure",
     "plugin-validator",
     "plugin-versioning",
-    "service-registry",
-    "startup-orchestrator",
-    "state-machine"
+    "---Dependencies & Packages---",
+    "dependency-resolution",
+    "package-artifact",
+    "package-registry",
+    "package-upgrade",
+    "---Metadata---",
+    "metadata-loader",
+    "metadata-persistence",
+    "metadata-plugin",
+    "metadata-customization",
+    "metadata-protection"
   ]
-}
+}

content/docs/references/kernel/meta.json

@@ -1,44 +1,51 @@
 {
   "title": "System Protocol",
   "pages": [
-    "app-install",
-    "audit",
-    "auth-config",
-    "cache",
-    "change-management",
-    "collaboration",
-    "compliance",
+    "---Runtime & Services---",
     "core-services",
-    "deploy-bundle",
-    "disaster-recovery",
-    "email-config",
-    "email-template",
-    "encryption",
-    "environment-artifact",
     "http-server",
-    "incident-response",
+    "worker",
     "job",
-    "license",
-    "logging",
-    "masking",
     "message-queue",
+    "cache",
+    "search-engine",
+    "object-storage",
+    "---Observability---",
+    "logging",
+    "metrics",
+    "tracing",
+    "audit",
+    "---Metadata & Migration---",
     "metadata-loader",
     "metadata-persistence",
-    "metrics",
     "migration",
-    "notification",
-    "object-storage",
-    "provisioning",
-    "registry-config",
-    "search-engine",
+    "change-management",
+    "---Security & Compliance---",
+    "auth-config",
     "security-context",
-    "settings-client",
-    "settings-manifest",
+    "encryption",
+    "masking",
+    "compliance",
     "supplier-security",
+    "---Tenancy & Provisioning---",
     "tenant",
-    "tracing",
-    "training",
+    "provisioning",
+    "app-install",
+    "license",
+    "registry-config",
+    "settings-manifest",
+    "settings-client",
+    "---Deployment & Operations---",
+    "deploy-bundle",
+    "environment-artifact",
+    "disaster-recovery",
+    "incident-response",
+    "---Communication & Localization---",
+    "notification",
+    "email-config",
+    "email-template",
+    "collaboration",
     "translation",
-    "worker"
+    "training"
   ]
-}
+}