feat: add EthereumWatcher and enhanced SolanaWatcher with signal validation

[andrewlfc7]

Summary

This PR introduces new multi-chain monitoring features and improves signal reliability in the Eremos framework.

What's Changed

• EthereumWatcher (Ξ)
  • New agent polling Ethereum L1 using ethers.js (HTTP RPC).
  • Emits high_block_activity when a block’s tx count exceeds threshold (default: 50).
• SolanaWatcher (◎)
  • Updated to HTTP polling only (removes logsSubscribe dependency for broader RPC compatibility).
  • Emits high_activity_detected when transaction logs exceed threshold (default: 5).
• Signal Validation
  • Added createSignal utility (utils/signal.ts).
  • Enforces required fields (type, hash, timestamp, source) to prevent malformed logs.
• Agent Runner Selection
  • Updated run-agents.ts to support CLI arg selection:

    npm run dev sol   # run SolanaWatcher only
    npm run dev eth   # run EthereumWatcher only
    npm run dev       # run all agents

---

Configuration

Update your .env.local to include both Solana and Ethereum RPC URLs:

# Solana RPC endpoint (Helius, Triton, or public)
SOLANA_RPC_URL="https://api.mainnet-beta.solana.com"

# Ethereum RPC endpoint (Infura, Alchemy, QuickNode, etc.)
ETH_RPC_URL="https://mainnet.infura.io/v3/<PROJECT_ID>"

# Optional overrides
POLL_INTERVAL=10000          # how often to poll the chain (ms)
ACTIVITY_THRESHOLD=5         # threshold for logging/logCount or txCount