add payment-method retrieve command to link-cli

[haoxuanxu-stripe]

Summary

Adds link-cli payment-methods retrieve for the new GET /payment-details/:id Link API endpoint.

• Adds retrieve support to the TypeScript and Go SDKs
• Adds CLI interactive and structured output
• Returns a clear NOT_FOUND error for missing payment methods
• Supports balance-backed payment method details
• Updates documentation and the payment credential skill
• Adds SDK, CLI, sanitization, and integration coverage

Test plan

• TypeScript type checks
• SDK unit tests
• CLI component tests
• CLI integration test using the built executable
• Biome checks
• Go tests (Go toolchain unavailable locally)