docs: add video-embedded getting-started pages for API Trigger, Webhook, Telephony, Tools & KB (#535)

* docs: add video-embedded getting-started pages for API Trigger, Webhook, Telephony, Tools & Knowledge Base

Four new tutorial pages inserted after Your First Agent in 5 Minutes, each
pairing a walkthrough video with a step-by-step practical guide sourced
from the recorded demo: Trigger Calls Automatically (API Trigger), Send
Call Data Back Automatically (Webhook), Connect Your Phone Number
(Twilio telephony), and Give Your Agent Real Data (HTTP tools + KB).

* docs: address greptile review feedback on PR #535

* docs: link Twilio Verified Caller IDs page directly

* Restructure the documents

* docs: embed agent builder walkthrough video on first-agent page

* docs: match link text to renamed Connect with Telephony title

* docs: warn that default outbound telephony config is required for API Trigger

---------

Co-authored-by: Abhishek Kumar <abhishek@a6k.me>

docs/getting-started/send-call-data-with-webhooks.mdx

@@ -0,0 +1,60 @@
+---
+title: "Sync Data using Webhook"
+description: "Get everything Dograh learned during the call back into your system the moment it ends."
+---
+
+The last page covered sending data into a call with API Trigger and `initial_context`. Now the opposite side: how Dograh sends what it learned back out to your system once the call ends.
+
+That extracted data lives in `gathered_context`. So the full picture is: `initial_context` is what your backend sends into the call, `gathered_context` is what Dograh extracts from it. A **Webhook** node is how you get `gathered_context` back out.
+
+<iframe
+  className="w-full aspect-video rounded-xl"
+  src="https://www.youtube.com/embed/w4XvzPWoFv4"
+  title="Dograh Webhook Node Explained, Get Call Data Into Your Backend"
+  allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
+  allowFullScreen
+></iframe>
+
+## Step 1: Add the node
+
+Click **Add node**, scroll down, and you'll find the **Webhook** node. Add it and open it up.
+
+## Step 2: Set the endpoint
+
+First thing you'll see is the endpoint URL. Paste your backend's webhook URL here. Still testing? Use a free URL from [webhook.site](https://webhook.site), copy your unique URL there and paste it into Dograh.
+
+Set the method to **POST**. If your backend needs auth, add a bearer token or API key right here too.
+
+## Step 3: Build the payload template
+
+This is the important part, it decides exactly what JSON Dograh sends. Include both kinds of context: `initial_context` fields like debtor name, client name, and debt amount, and `gathered_context` fields like amount to pay, payment method, and sentiment.
+
+```json
+{
+  "debtor_name": "{{initial_context.debtor_name}}",
+  "client_name": "{{initial_context.client_name}}",
+  "debt_amount": "{{initial_context.debt_amount}}",
+  "amount_user_will_pay": "{{gathered_context.amount_user_will_pay}}",
+  "payment_method": "{{gathered_context.payment_method}}",
+  "sentiment": "{{gathered_context.sentiment}}"
+}
+```
+
+<Warning>
+Variable names in your payload have to match your context fields exactly. If a variable cannot be resolved, its field remains in the payload with an empty string value.
+</Warning>
+
+## Step 4: Save and publish
+
+Save the webhook node, then publish the agent.
+
+## Step 5: Test it
+
+Run a test call. When it ends, go back to your webhook receiver. You'll see one request with both `initial_context`, the data you sent into the call, and `gathered_context`, what Dograh extracted from the conversation, sitting in the same JSON payload.
+
+That's the complete loop: your backend sends `initial_context` into Dograh, Dograh runs the call and extracts `gathered_context`, and the webhook node sends the final structured data back to your backend. For production, swap the webhook.site URL for your real backend URL.
+
+## Next Steps
+
+- **Connect a real phone number**: [Connect with Telephony](/getting-started/connect-telephony) covers hooking up Twilio so these calls go out for real.
+- **Full variable list and authentication options**: see the [Webhook reference](/voice-agent/webhook) and the [Webhook Payloads developer reference](/developer/webhooks).