fix(assets-controllers): refetch snap balances after vault unlock when fetch was skipped while locked

[khanti42]

Explanation

• Subscribe to KeyringController:stateChange in MultichainBalancesController.
• When the vault transitions from locked → unlocked, call updateBalance for any snap-backed (non-EVM) account that still has no cached balance entries.

Problem

MultichainAssetsController:accountAssetListUpdated triggers balance fetches only when KeyringController:getState().isUnlocked is true. If that event fires while the vault is locked, the fetch is skipped and never retried after unlock, so the UI can show empty multichain token rows despite assets in MultichainAssetsController state.

Consumer note

Extension (and any other consumer) must allow KeyringController:stateChange on the MultichainBalancesController restricted messenger; otherwise this subscription will not receive events.

References

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
Adds a new KeyringController:stateChange subscription and triggers balance refetches on unlock, which can change runtime behavior and requires consumers to allow an additional messenger event.

Overview
Ensures MultichainBalancesController retries fetching balances after a vault unlock by subscribing to KeyringController:stateChange and, on a locked→unlocked transition, calling updateBalance for non-EVM accounts that still have no cached balances.

Updates the controller’s allowed messenger events (and test messenger delegation) to include KeyringController:stateChange, and documents the fix in the assets-controllers changelog.

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Unlock handler skips accounts with existing partial balances

Medium Severity

The hasBalance check only triggers updateBalance for accounts with a completely empty balance map. Since balances state is persisted (persist: true), an account can have existing balance entries from a prior session while new assets get added via accountAssetListUpdated while locked. On unlock, the account already has entries so hasBalance is true, and the newly-added assets never get their balances fetched — the exact scenario this PR aims to fix, but only partially addressed.

 

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