fix: run RPC fallback on Accounts API poll updates

[salimtb]

The stale-balance re-read only ran in the forced getAssets fast pipeline, so while the wallet sat open, 30s Accounts API polls kept committing responses that omit unindexed tokens with a plain merge — the stale amount survived until the next forced refresh (unlock, transaction, manual refresh).

handleAssetsUpdate now inserts RpcFallbackMiddleware into the enrichment pipeline for AccountsApiDataSource updates, after graduation and before detection, mirroring the fast pipeline. WebSocket updates are excluded (incremental single-asset pushes — absence is not staleness) and RPC/Snap updates are excluded so RPC never re-triggers itself.

Explanation

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

---

Note

Medium Risk
Touches the live balance merge path for Accounts API polls and adds extra RPC reads when indexed tokens are omitted; scope is limited by source gating and existing fallback rules.

Overview
Fixes stale token balances that could persist while the wallet stayed open: periodic Accounts API polls merge responses that omit unindexed tokens, and RpcFallbackMiddleware previously ran only on the forced getAssets fast path.

handleAssetsUpdate now runs RpcFallbackMiddleware for AccountsApiDataSource updates in the enrichment pipeline (after custom-asset graduation, before detection), so tracked assets missing from a poll response are re-read on-chain via RPC. WebSocket (AccountActivityDataSource), RPC, and Snap updates are unchanged and do not trigger the fallback.

Adds a unit test that asserts poll updates pass omitted tracked assets as customAssets to RPC, and that WebSocket updates do not invoke the fallback. Changelog updated under Fixed.

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[salimtb]

@cursor fix the conflict

[cursor]

I've successfully resolved the merge conflict in the CHANGELOG.md file. Here's what I did:

Conflict Resolution:

• The conflict was between two stale balance fixes in the changelog
• Both entries were important and needed to be preserved:
  1. fix: run RPC fallback on Accounts API poll updates #10078: RPC fallback on poll updates (your PR's fix)
  2. feat: bypass Accounts API server cache after transaction confirmation #10068: bypassServerCache on transaction confirmation (from main branch)
• I merged both entries under the ### Fixed section, maintaining proper changelog formatting

Changes Made:

• Resolved the conflict in packages/assets-controller/CHANGELOG.md
• Staged and committed the merge with a descriptive message
• Pushed the resolved merge to origin/fix/fix-polling-fallback

The PR now includes the latest changes from main and the conflict has been resolved. The branch is ready for review.