docs(examples): add CDP integration end-to-end test harness

[amiecorso]

Summary

• New examples/cdp-integration-test/ directory with a two-step TypeScript harness that exercises the full CDP integration with SpendRouter against a local cdp-service stack and Base Sepolia.
• Step 1 creates an EOA + smart wallet + spend permission, then verifies the cdp-service substitution (spender = SpendRouter, extraData = encoded routing) and the SDK dispatch decision synchronously.
• Step 2 uses the EOA executor to actually call SpendRouter.spendAndRoute() onchain, decoding the resulting tx to prove the SDK targeted the right contract.
• Reference run produced a successful Base Sepolia tx 0x6025f0bf... where to = SpendRouter, function = spendAndRoute.

Context

Used as pre-release verification for the CDP SpendRouter integration work. Local-stack setup, methodology, and gaps documented in the Coinbase-internal wiki writeup linked from the harness README.

Open as draft

Marking as draft — this is for internal verification/onboarding, not active maintenance. Happy to convert to ready-for-review or close depending on the team's preference for examples in this repo.

[cb-heimdall]

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