feat: add versioned wallet discovery output

[dmarzzz]

Summary

Adds an opt-in, versioned machine-readable wallet discovery contract:

kohaku list-wallets --format json-v1

The response is a single JSON document with:

• kind: "kohaku-cli/wallet-list"
• version: 1
• a deterministically ordered wallet array
• normalized network
• numeric chainId
• CAIP-2 caip2

This is intentionally a narrow first increment. Stable wallet IDs and versioned output for creation/address allocation can follow after the envelope is reviewed.

Compatibility

• Existing interactive output is unchanged.
• Existing list-wallets --non-interactive JSON is unchanged.
• The new contract is used only when --format json-v1 is supplied.
• Wallet ordering uses a locale-independent UTF-16 total order.

Verification

• TypeScript typecheck
• Full test suite: 302 tests across 113 suites
• Production build
• git diff --check
• Tests cover empty/mixed-network listings, legacy output, option validation, and case-variant ordering

Relates to #44.