Fix msig:propose serialization for non-name fields

[paulgnz]

Summary

• Fixes msig:propose failing with "Name should be less than 13 characters" when proposing transactions with u64/u128 action fields (e.g. poolId: 265)
• Root cause: api.transact() recursively re-serializes already-serialized action data in the nested trx field, treating hex strings as structured JSON
• Fix: manually serialize the inner transaction and propose data to raw bytes after api.serializeActions(), bypassing recursive serialization

Reproduction

proton msig:propose myproposal '[{"account":"simpledex","name":"forcerempool","data":{"poolId":265},"authorization":[{"actor":"protonnz","permission":"active"}]}]' 'simplesetup@active'
# Before: Error: Name should be less than 13 characters
# After: Multisig myproposal successfully proposed.

Test plan

• Build succeeds (npm run build)
• Tested on Proton mainnet: msig:propose with simpledex::forcerempool({poolId: 265}) — proposal created successfully
• msig:approve and msig:exec unchanged (no nested transactions)

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