docs: add chat-agent example projects and Infisical Secret Sync

docs: add the Ask Trigger and ElevenLabs Voice agent example projects,
and document the native Infisical Secret Sync

- Two new example-project pages under Guides & examples: **Ask Trigger
chat agent** (a `chat.agent()` that teaches Trigger.dev by drawing
interactive node-graphs, quizzes and cards with json-render, grounded on
live docs via MCP) and **ElevenLabs Voice agent** (a spoken-conversation
assistant with streaming ElevenLabs STT/TTS, server-side VAD, and Head
Start for a fast first reply).
- Documented the native **Infisical Secret Sync** on the
environment-variables page, alongside the existing `syncEnvVars`
build-extension pattern.

Mono-RevId: 157f7fa58eb818c1105ddfe81863b1d9a9c0e6ee

Author: D-K-P

docs/config/extensions/syncEnvVars.mdx

@@ -63,6 +63,12 @@ export default defineConfig({
 
 In this example we're using env vars from [Infisical](https://infisical.com).
 
+<Tip>
+  Infisical also offers a native [Secret Sync](/deploy-environment-variables#infisical-secret-sync)
+  that pushes secrets to Trigger.dev without a build extension or a redeploy. Use `syncEnvVars` when
+  you want to resolve secrets at deploy time in code, or for a service without a native sync.
+</Tip>
+
 ```ts trigger.config.ts
 import { defineConfig } from "@trigger.dev/sdk";
 import { syncEnvVars } from "@trigger.dev/build/extensions/core";

docs/deploy-environment-variables.mdx

@@ -184,14 +184,35 @@ For more information about the context object, see the [Context documentation](/
 
 ### Sync env vars from another service
 
-You could use the SDK functions above but it's much easier to use our `syncEnvVars` build extension in your `trigger.config` file.
+There are two ways to pull secrets from another service into Trigger.dev: a native **Secret Sync** (currently [Infisical](https://infisical.com)), or the `syncEnvVars` build extension for any other service.
+
+#### Infisical Secret Sync
+
+If your secrets live in [Infisical](https://infisical.com), sync them natively, without a build extension or a redeploy. You configure the sync in the Infisical dashboard, and it pushes secrets straight to your [Environment Variables page](#in-the-dashboard) in Trigger.dev. When a secret changes in Infisical the sync updates the matching variable, and your tasks pick up the new value on their next run.
+
+Set it up in Infisical in two steps:
+
+1. Add a **Trigger.dev App Connection** using a Trigger.dev Personal Access Token from your account settings. Self-hosted instances are supported.
+2. Create a **Secret Sync**: choose the connection, pick the target organization, project and environment (Production, Staging, Development, or Preview), and set the secret path to sync.
+
+Follow the [Trigger.dev Secret Sync guide](https://infisical.com/docs/integrations/secret-syncs/trigger-dev) in the Infisical docs for the full walkthrough.
+
+<Note>
+  A Secret Sync only overwrites the keys it manages, leaving variables you set manually untouched.
+  Synced variables are marked as [secret](#secret-environment-variables) by default, so they appear
+  redacted on the Environment Variables page.
+</Note>
+
+#### Using the `syncEnvVars` build extension
+
+For any other service, use our `syncEnvVars` build extension in your `trigger.config` file to resolve secrets at deploy time.
 
 <Note>
   To use the `syncEnvVars` build extension, you should first install the `@trigger.dev/build`
   package into your devDependencies.
 </Note>
 
-In this example we're using env vars from [Infisical](https://infisical.com).
+In this example we're using env vars from [Infisical](https://infisical.com), but you can adapt it to any secrets manager.
 
 ```ts trigger.config.ts
 import { defineConfig } from "@trigger.dev/sdk";

docs/docs.json

@@ -538,12 +538,14 @@
             "group": "Example projects",
             "pages": [
               "guides/example-projects/anchor-browser-web-scraper",
+              "guides/example-projects/ask-trigger-chat-agent",
               "guides/example-projects/batch-llm-evaluator",
               "guides/example-projects/claude-changelog-generator",
               "guides/example-projects/claude-github-wiki",
               "guides/example-projects/claude-thinking-chatbot",
               "guides/example-projects/clickhouse-chat-agent",
               "guides/example-projects/cursor-background-agent",
+              "guides/example-projects/elevenlabs-voice-agent",
               "guides/example-projects/human-in-the-loop-workflow",
               "guides/example-projects/mastra-agents-with-memory",
               "guides/example-projects/meme-generator-human-in-the-loop",