feat(examples): add Telegram x402 paid-question bot

examples/telegram-x402-bot/.env.example

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+TELEGRAM_BOT_TOKEN=replace_with_botfather_token
+X402_PAY_TO=G_YOUR_STELLAR_ADDRESS
+X402_PRICE=0.02
+X402_NETWORK=stellar:testnet
+X402_FACILITATOR_URL=https://facilitator.x402.org
+NIRIUM_API_URL=https://nirium-agent.fly.dev
+NIRIUM_API_KEY=replace_if_required

examples/telegram-x402-bot/README.md

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+# Telegram x402 paid-question bot
+
+A minimal Telegram bot that gates Nirium agent answers behind a 0.02 USDC
+Stellar x402 payment. It never answers the protected question until the
+facilitator has both verified and settled the submitted signature.
+
+## Setup
+
+1. Create a Telegram bot with BotFather and copy `.env.example` to your local
+   environment manager.
+2. Set `TELEGRAM_BOT_TOKEN` and your Stellar settlement address in
+   `X402_PAY_TO`. Never commit either value.
+3. Install and run:
+
+```bash
+npm install
+npm run build
+npm start
+```
+
+## Usage
+
+```text
+/ask What is the current Nirium market snapshot?
+```
+
+The bot responds with a machine-readable x402 challenge. After a client signs
+the payment, submit:
+
+```text
+/paid <x402-signature> What is the current Nirium market snapshot?
+```
+
+Invalid or unsettled signatures receive `402 Payment Required`. Successful
+settlement unlocks the answer and includes the settlement transaction when the
+facilitator returns one.
+
+## Development
+
+```bash
+npm test
+npm run typecheck
+```
+
+Tests mock the facilitator; they never spend funds or contact Stellar.