fix(AssetController): refactor Snap data source

[Kriys94]

Explanation

This PR simplifies and cleans up SnapDataSource by:

1. Dynamic snap discovery via PermissionController: Instead of hardcoded snap registry entries, SnapDataSource now dynamically discovers installed snaps that have the endowment:keyring permission and extracts their supported chain IDs from permission caveats. This makes the data source more flexible and extensible for future snaps.

2. Simplified fetch routing: Changed from complex chain-based routing to account-based routing using account.metadata.snap.id. This aligns with how MultichainBalancesController handles snap accounts and is more direct since each account already knows which snap it belongs to.

3. Added KeyringClient: Replaced manual SnapController:handleRequest calls with KeyringClient from @metamask/keyring-snap-client, which provides cleaner typed methods (listAccountAssets, getAccountBalances). This follows the same pattern used in MultichainBalancesController.

4. Removed unused/redundant code:

   • Removed DEFAULT_SNAP_POLL_INTERVAL constant (never used)
   • Removed #groupChainsBySnapId method (no longer needed with account-based routing)
   • Removed #fetchFromSnapById method (inlined into fetch)
   • Removed #accountSupportsChain method (unused after simplification)
   • Removed redundant chain filtering in fetch (already done by middleware/subscribe callers)
   • Removed unused InternalAccount import

5. Used proper types: Replaced inline type Record<string, { amount: string; unit: string }> with GetAccountBalancesResponse and Balance from @metamask/keyring-api.

Dependencies added:

• @metamask/keyring-api: For Balance and CaipAssetType types
• @metamask/keyring-snap-client: For KeyringClient to make typed snap calls

References

• Related to the SnapDataSource dynamic snap discovery refactoring
• Pattern aligned with MultichainBalancesController and MultichainAssetsController implementations

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

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Note

Medium Risk
Moderate risk: replaces core snap discovery/routing logic and the snap-call transport, which can change which chains/accounts are handled and how balances are fetched/filtered.

Overview
SnapDataSource is refactored from a hardcoded Solana/Bitcoin/Tron registry to dynamic snap discovery: it now queries SnapController:getRunnableSnaps and PermissionController:getPermissions to find keyring snaps (endowment:keyring) and derive supported chainIds from the endowment:assets caveat, populating activeChains and a new chainToSnap map.

Balance fetching is simplified to be account-driven using account.metadata.snap.id and KeyringClient (via SnapController:handleRequest) instead of direct wallet_getSnaps/wallet_invokeSnap calls; related chain-management APIs/exports for predefined networks and snap types are removed. Messenger initialization is updated to delegate the new Snap/Permission controller actions, and tests are rewritten accordingly. Dependencies/tsconfig are updated to include the keyring and permission/snaps packages.

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[FrederikBolding]

I don't fully understand how this is supposed to work. What if the chainToSnap mapping isn't already populated? Are the inputs BIP-44 account groups or individual accounts?

[Kriys94]

chainToSnap is populated at the initialization of MetaMask, much before that we are fetching assets. So What if the chainToSnap mapping isn't already populated? is unlikely to say impossible.

Are the inputs BIP-44 account groups or individual accounts?
request.accounts is the selected account group

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

[Prithpal-Sooriya]

Approving on first pass. This data source is completely new and not in production (we have time to refine).

Lets have the snaps team to review before merging. Maybe a short loom/recording to walkthrough changes?