Add smart-wallets recipe: session keys + viem account end-to-end example

[marcos-golem]

Every [ ARKIV ] quickstart today shows privateKeyToAccount pulling a raw key from .env. That is not the production path for agents, dApps, or any builder moving past prototype — yet there is no worked example showing the smart-wallet pattern. The SDK already accepts any viem-compatible account, so the capability exists; it is just invisible.

What: Add a recipes/smart-wallets/ page with one fully worked, end-to-end example covering:

• Connecting a smart-wallet account to the [ ARKIV ] SDK
• Creating a session key scoped to an [ ARKIV ] operation
• Creating and mutating an entity using that session key
• Handling entity expiration correctly (expiration is scheduled at write time, not enforced by teardown)

How:

• Choose the canonical wallet partner for the worked example (see open decision below)
• Write the end-to-end code example against that partner's SDK + viem adapter
• Add a short paragraph at the top of the page noting where Safe, Privy, and Coinbase Smart Wallet diverge — so builders using a different stack have a starting point without a full second recipe
• Add a cross-link from the existing quickstart page ("Ready for production? See the smart-wallets recipe") at the point where privateKeyToAccount is introduced
• Validate the example compiles and runs against the current SDK version before merging

Open decision — wallet partner choice:

The recipe needs one canonical example. Three candidates:

Partner	Notes
Safe	Broadest ecosystem recognition; session-key support via Safe{Core} AA SDK; more setup steps
Privy	Lowest onboarding friction for builders new to AA; embedded-wallet story maps well to agent use cases
Coinbase Smart Wallet	Strong Base/Ethereum alignment; simple viem adapter; narrower audience

Input needed from whoever owns wallet partnerships before work begins.

[marcos-golem]

Check which "partner" is the most widely used and start there.