feat(tempo): add resolveAccount hooks

[parvahuja]

Summary

• add a shared resolveAccount hook for Tempo charge and session account selection
• resolve charge accounts from executable calls, omitting calls when auto-swap routing is account-dependent
• derive session voucher authority from the selected account and support primitive access-key voucher signatures

Testing

• VITE_TEMPO_NETWORK=none pnpm exec vp test --run src/tempo/client/Charge.test.ts src/tempo/session/client/Session.test.ts src/tempo/session/precompile/Voucher.test.ts src/tempo/session/client/CredentialState.test.ts
• pnpm check:types
• pnpm check:ci

[pkg-pr-new]

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npm i https://pkg.pr.new/mppx@579

commit: 95251e4

[brendanjryan]

LGTM