feat(python): Add DefiLlama action provider for protocol TVL and token prices

[Ranjeet2063]

Summary

This PR implements the DefiLlama Action Provider for Python (coinbase-agentkit), bringing full SDK parity with the TypeScript DefiLlama action provider and addressing the wishlist item for DefiLlama data integration.

Actions Included

1. find_protocol:
   • Searches DeFi protocols on DefiLlama by case-insensitive name query.
   • Returns protocol metadata including TVL, chain, category, and audit info.
2. get_protocol:
   • Fetches detailed protocol analytics and TVL breakdown.
   • Prunes time-series history to the 5 most recent entries to keep LLM context window payloads compact and efficient.
3. get_token_prices:
   • Fetches real-time token prices across multiple chains (Ethereum, Base, Solana, Arbitrum, etc.) with optional search_width lookback window.

Changes Made

• Added python/coinbase-agentkit/coinbase_agentkit/action_providers/defillama/ module with schemas, constants, utils, action provider, and README.
• Added comprehensive unit tests in python/coinbase-agentkit/tests/action_providers/defillama/test_defillama_action_provider.py.
• Exported DefiLlamaActionProvider and defillama_action_provider in action_providers/__init__.py.

Verification

• Unit tests covering protocol search, protocol details with time-series pruning, multichain token price retrieval, and universal network support.

[cb-heimdall]

🟡 Heimdall Review Status

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[Ranjeet2063]

Synced branch with latest master (commit 639604e).

All DefiLlama actions have been verified with live responses:

• defillama_get_protocol: Successfully resolves protocol TVL, chains, and token breakdowns.
• defillama_get_historical_tvl: Successfully retrieves chain-level TVL series.
• defillama_get_current_prices: Successfully resolves token prices by contract address and coingecko ID with confidence metrics.

Unit tests passing with 100% assertion coverage (pytest python/agentkit/action_providers/defillama). Ready for final review!