fix: preserve token icons when balance API fails

[mj-kiwi]

Description

Token metadata and balance are currently fetched in parallel by AccountApiClient. When the Account API balance request fails, for example with HTTP 403, the rejected balance promise causes the
entire Promise.all to reject. The metadata request may have succeeded, but the token metadata service then falls back to the blockchain client, which cannot provide token icon URLs.

This change makes balance resolution independent from metadata resolution:

• Treats balance request failures as an unavailable balance instead of rejecting the combined request.
• Preserves token metadata and icon URL resolution when the balance API fails.
• Skips balance and fiat balance rendering when no balance is available.
• Keeps metadata failures and unsupported-chain fallback behavior unchanged.
• Adds regression coverage for a 403 balance response with successful metadata and icon data.

Related issues

Fixes: #

Manual testing steps

1. Build and run the Gator Permissions Snap and the development site.
2. Open the development site at http://localhost:8000.
3. Request an ERC-20 permission for a token supported by the Token Metadata API.
4. Confirm the MetaMask permission confirmation dialog displays the token symbol and icon even when the Account API balance request returns an error.
5. Confirm that the permission confirmation flow does not fail when the balance is unavailable.

Automated verification:

• yarn workspace @metamask/gator-permissions-snap test test/client/accountApiClient.test.ts test/services/tokenMetadataService.test.ts test/core/confirmation/ConfirmationShell.test.ts --runInBand
• yarn eslint packages/gator-permissions-snap/src/clients/accountApiClient.ts packages/gator-permissions-snap/src/clients/types.ts packages/gator-permissions-snap/src/core/confirmation/ConfirmationShell.ts packages/gator-permissions-snap/test/client/accountApiClient.test.ts

Screenshots/Recordings

Before

The Account API balance request failure caused the combined balance and metadata request to reject, so the flow fell back to the blockchain client and the token icon was unavailable.

After

The balance failure is treated as an unavailable balance. Token metadata and the icon URL continue to resolve independently.

Pre-merge author checklist

• I've followed MetaMask 7715 Permissions Snaps Contributor Docs and MetaMask 7715 Permissions Snaps Coding
  Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

---

Note

Low Risk
Scoped to permission confirmation token display and Account API error handling; grant logic is unchanged and metadata failures still propagate as before.

Overview
When the Account API balance call fails (e.g. HTTP 403), getTokenBalanceAndMetadata no longer rejects the combined fetch: the balance promise is caught, logged, and resolved as balance: undefined, while metadata (including iconUrl) still completes via Promise.all.

The confirmation flow treats a missing balance as unavailable rather than a hard failure: ConfirmationShell sets tokenBalanceUnavailable, skips token/fiat formatting, and ConfirmationShellContent hides the balance row instead of showing loading skeletons. TokenBalanceAndMetadata.balance is typed as bigint | undefined, with client and shell tests updated for partial success and unavailable-balance UI.

^{Reviewed by Cursor Bugbot for commit 1460d94. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cursor]

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

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, have a team admin enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 4d5776f. Configure here.}