Feat: Existing permissions banner with list

[mj-kiwi]

Description

This PR improves the permission confirmation experience when a dApp origin already has active (non-revoked) granted permissions stored in profile sync.

User-facing behavior

• Shows an informational or warning banner when existing permissions are detected, with copy that distinguishes similar (same broad category: stream vs periodic) vs dissimilar permissions.
• Adds a “Review them” action that swaps the confirmation UI to a read-only list of existing permissions (grouped by account, with formatted token amounts where applicable) and a Continue control to return to the normal grant flow.

Implementation notes

• Introduces ExistingPermissionsService and supporting UI (existingPermissionsContent, PermissionCard, permissionFormatter) integrated via PermissionRequestLifecycleOrchestrator and PermissionHandler (event handlers for show/hide existing-permissions views).
• Prefetches existing-permissions status in parallel with the introduction flow to avoid blocking the first paint of confirmation content.
• Follow-up hardening: optional showExistingPermissions on BaseContext (avoids requiring every buildContext to set it); suffix-based stream/periodic categorization (-stream / -periodic); structured logger usage on storage failures and debug logging when token metadata formatting fails; aligned extractDescriptorName import with the rest of the snap; removed unused constructor dependency; fixed invalid barrel type export; expanded unit tests (existingPermissionsService, permissionFormatter).

Related issues

Fixes:

Manual testing steps

1. yarn prepare:snap (if needed), yarn build, then yarn start and open the dev site (e.g. http://localhost:8000) with MetaMask Flask and the local snaps (kernel / gator) connected.
2. Grant a permission to the test origin for a stream- or periodic-type permission, then trigger another permission request from the same origin:
   • Confirm a banner appears (warning vs info depending on similar vs dissimilar case).
3. Click “Review them” and verify the existing permissions list renders (accounts, chains, amounts/labels as expected); click Continue and confirm you return to the standard confirmation UI.
4. Cancel / complete the flow and confirm no crashes or unhandled rejections when dismissing during intro (existing-permissions status promise should not reject the lifecycle).

Screenshots/Recordings

Before

After

Screen.Recording.2026-03-23.at.3.58.00.PM.mov

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.

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Note

Medium Risk
Changes the permission confirmation UI flow and orchestration (including async updates and button handling), which could impact users’ ability to grant/cancel requests if edge cases regress. Data/security impact is limited since it only reads stored grants and adjusts UI/state.

Overview
Adds an existing-permissions banner + review subview to the permission confirmation experience: when stored non-revoked grants exist for the requesting origin, the confirmation screen shows an info/warning banner (similar vs dissimilar stream/periodic) with a Review them action that swaps to a read-only, account-grouped list of existing permissions and a Back to request control.

Refactors confirmation rendering so the footer grant/cancel buttons live inside PermissionHandlerContent (not ConfirmationDialog), and updates the orchestrator to prefetch a single profile-sync snapshot for both banner state and list rendering, with skeleton + fallback UI and improved logging/error handling. Updates permission formatting/display (PermissionCard, permissionFormatter) to support structured labeled fields and token-amount formatting, and expands tests to cover status classification, formatting behavior, and failure paths.

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[jeffsmale90]

Looking great!

I think it would be good if we could reduce the refetches of existing granted permissions, as they shouldn't ever change during the lifecycle of a permissions request.

[jeffsmale90]

lgtm!