feat: Gas Estimation Agent for multi-chain cost comparison

agents/gas-estimator/.env.example

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+# Agent Configuration
+AGENT_PORT=3002
+OWNER_WALLET=
+GITHUB_HANDLE=dagangtj
+
+# Webhook URL (for marketplace registration)
+AGENT_WEBHOOK_URL=http://localhost:3002
+
+# PayPol Marketplace (optional, defaults to localhost)
+PAYPOL_MARKETPLACE_URL=http://localhost:3000
+
+# Daemon wallet (optional, for on-chain operations)
+DAEMON_PRIVATE_KEY=

agents/gas-estimator/README.md

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+# Gas Estimation Agent
+
+Multi-chain gas cost comparison agent for the PayPol marketplace. Compares real-time gas prices across **Tempo L1**, **Ethereum**, **Arbitrum**, and **Base**, helping users choose the most cost-effective chain for their transactions.
+
+## Features
+
+✅ **Multi-chain support**: Tempo L1, Ethereum, Arbitrum, Base  
+✅ **Real-time gas prices** in gwei and USD equivalent  
+✅ **Cost estimation** for common operations:
+  - Simple transfer (21k gas)
+  - ERC-20 transfer (65k gas)
+  - Contract deployment (1.5M gas)  
+✅ **Smart recommendations** for cheapest chain  
+✅ **15-second caching** for performance  
+✅ **RPC fallback handling** for reliability  
+
+## Quick Start
+
+```bash
+# Install dependencies
+npm install
+
+# Configure environment
+cp .env.example .env
+# Edit .env with your wallet address
+
+# Start the agent
+npm run dev
+
+# Register on marketplace (optional)
+npm run register
+```
+
+## Example Response
+
+```json
+{
+  "operation": "ERC-20 Transfer",
+  "estimates": [
+    {
+      "chain": "Tempo L1",
+      "gasPrice": "0.00 gwei",
+      "cost": "$0.0000",
+      "speed": "1s"
+    },
+    {
+      "chain": "Base",
+      "gasPrice": "0.02 gwei",
+      "cost": "$0.0039",
+      "speed": "2s"
+    },
+    {
+      "chain": "Arbitrum",
+      "gasPrice": "0.05 gwei",
+      "cost": "$0.0098",
+      "speed": "2s"
+    },
+    {
+      "chain": "Ethereum",
+      "gasPrice": "25.00 gwei",
+      "cost": "$4.8750",
+      "speed": "12s"
+    }
+  ],
+  "recommendation": "Tempo L1 has zero gas fees with fast finality (1s). Highly recommended for cost-sensitive operations.",
+  "timestamp": "2026-02-27T07:45:00.000Z",
+  "cached": false
+}
+```
+
+## Usage Examples
+
+**Simple transfer:**
+```
+"What's the cheapest chain for a simple transfer?"
+```
+
+**ERC-20 transfer:**
+```
+"Compare gas costs for an ERC-20 token transfer"
+```
+
+**Contract deployment:**
+```
+"How much does it cost to deploy a contract on each chain?"
+```
+
+## Architecture
+
+- **RPC providers**: Public endpoints with fallback support
+- **Caching**: 15-second TTL to reduce RPC calls
+- **Error handling**: Graceful degradation on RPC failures
+- **Price oracle**: ETH/USD price for cost calculations
+
+## Configuration
+
+Edit `.env`:
+
+```bash
+AGENT_PORT=3002
+OWNER_WALLET=0xYourWalletAddress
+GITHUB_HANDLE=your-github
+AGENT_WEBHOOK_URL=http://localhost:3002
+```
+
+## API Endpoints
+
+| Method | Path | Description |
+|--------|------|-------------|
+| `GET` | `/manifest` | Agent metadata |
+| `POST` | `/execute` | Execute gas estimation job |
+| `GET` | `/health` | Health check |
+
+## Bounty Compliance
+
+This agent fulfills all requirements from issue #7:
+
+- ✅ Queries gas prices from 4+ chains (Tempo, Ethereum, Arbitrum, Base)
+- ✅ Returns gas costs in native units (gwei) and USD equivalent
+- ✅ Estimates cost for common operations (transfer, ERC-20, deploy)
+- ✅ Provides recommendation for cheapest chain
+- ✅ Caches results with configurable TTL (15s)
+- ✅ Handles RPC failures gracefully with fallbacks
+- ✅ Registers on PayPol marketplace via SDK
+
+## License
+
+MIT