fix: marinade multisig dapp requests by preserving original message bytes

[taran-a]

Explanation

Fixes multisig dapp transaction signing by preserving the original transaction payload for external dapp origins.

• Decode dapp-origin signTransaction and signAndSendTransaction requests as transactions directly, whether the payload is a full serialized transaction or a bare compiled transaction message.
• Append only the snap account's signature, preserving existing signatures, compiled messageBytes, account ordering, and instruction account indices.
• Keep the existing MetaMask-origin signing flow unchanged.
• Add coverage for codec decoding, signer byte preservation, and wallet origin handling.

References

• Fixes WPN-1035

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

[taran-a]

@metamaskbot publish-preview

[github-actions]

Preview builds have been published. Learn how to use preview builds in other projects.

Expand for full list of packages and versions.

@metamask-previews/bitcoin-wallet-snap@2.0.1-preview-c5b54f00
@metamask-previews/snap-networks-utils@1.0.0-preview-c5b54f00
@metamask-previews/solana-wallet-snap@6.0.0-preview-c5b54f00
@metamask-previews/tron-wallet-snap@3.1.0-preview-c5b54f00

[Copilot]

Pull request overview

This PR updates @metamask/solana-wallet-snap transaction signing for external (dapp) origins to preserve the original transaction/message bytes during partial signing, which is necessary for multisig workflows that depend on an unchanged signing payload.

Changes:

• Add an origin-based switch in WalletService to request message-byte preservation for non-MetaMask origins when signing / signing+sending.
• Extend Signer.partiallySignBase64String with a preserveMessageBytes flag and add a codec path to wrap bare compiled message bytes into a Transaction shape without altering messageBytes.
• Add/extend Jest coverage for codec decoding and byte-preservation behavior; update snap manifest shasum and changelog.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/solana-wallet-snap/src/core/services/wallet/WalletService.ts	Passes an origin-derived preserveMessageBytes flag into the signer for sign + signAndSend flows.
packages/solana-wallet-snap/src/core/services/wallet/WalletService.test.ts	Adds assertions that MetaMask origin does not request preservation, while dapp origins do.
packages/solana-wallet-snap/src/core/services/signer/Signer.ts	Implements the preservation path by decoding to a Transaction directly and signing without message mutation.
packages/solana-wallet-snap/src/core/services/signer/Signer.test.ts	Adds coverage asserting messageBytes are preserved when requested.
packages/solana-wallet-snap/src/core/sdk-extensions/codecs.ts	Adds decoding for compiled message bytes into a Transaction shape and a new “unknown base64 → transaction” helper.
packages/solana-wallet-snap/src/core/sdk-extensions/codecs.test.ts	Adds tests for compiled-message wrapping and full-transaction decode without changing bytes.
packages/solana-wallet-snap/snap.manifest.json	Updates bundle shasum to match the new build output.
packages/solana-wallet-snap/CHANGELOG.md	Adds an Unreleased entry documenting the behavioral change.

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[Battambang]

lgtm