fix: use accounts sdk managed wallet keys

[alexrisch]

Summary

• route request payments through the accounts SDK provider instead of reconstructing access-key accounts from wallet store state
• preserve accounts SDK managed key material in wallet state parsing
• report managed keys with local signing material as pending/ready instead of unusable

Test plan

• pnpm exec tsc -b --noEmit
• pnpm vitest run test/wallet-store.test.ts test/identity.test.ts test/request.test.ts

Note: CLI_REFERENCE.md is intentionally left untracked and not included.