Docs: add nav titles across docs (#5689)

docs/plugins/agent-tools.md

@@ -3,6 +3,7 @@ summary: "Write agent tools in a plugin (schemas, optional tools, allowlists)"
 read_when:
   - You want to add a new agent tool in a plugin
   - You need to make a tool opt-in via allowlists
+title: "Plugin Agent Tools"
 ---
 
 # Plugin agent tools

docs/plugins/manifest.md

@@ -3,6 +3,7 @@ summary: "Plugin manifest + JSON schema requirements (strict config validation)"
 read_when:
   - You are building a OpenClaw plugin
   - You need to ship a plugin config schema or debug plugin validation errors
+title: "Plugin Manifest"
 ---
 
 # Plugin manifest (openclaw.plugin.json)

docs/plugins/voice-call.md

@@ -3,6 +3,7 @@ summary: "Voice Call plugin: outbound + inbound calls via Twilio/Telnyx/Plivo (p
 read_when:
   - You want to place an outbound voice call from OpenClaw
   - You are configuring or developing the voice-call plugin
+title: "Voice Call Plugin"
 ---
 
 # Voice Call (plugin)

docs/plugins/zalouser.md

@@ -3,6 +3,7 @@ summary: "Zalo Personal plugin: QR login + messaging via zca-cli (plugin install
 read_when:
   - You want Zalo Personal (unofficial) support in OpenClaw
   - You are configuring or developing the zalouser plugin
+title: "Zalo Personal Plugin"
 ---
 
 # Zalo Personal (plugin)