feat:getPublicClient() for EvmWalletProviders (ts) and custom RPC_URL (ts,python)

[phdargen]

Description

Implements improvements for PublicClient

• adds getPublicClient() method for EvmWalletProviders for convenient use in action providers
• uses getPublicClient() to simplify Truemarkets and flauch actions
• adds optional config for custom RPC_URL, useful eg to avoid rate limits or use flashblocks
• updates main chatbot examples with new optional RPC_URL config

Tests

Tested langchain-cdp-chatbot with custom RPC_URL and verified endpoint is called in alchemy dashboard

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1