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