Recovery discovery misses undeployed accounts funded only in native USDC #563

Problem

The first-run recovery scan decides whether an undeployed (counterfactual) account has been used by probing ERC-20 balances. It probes the wallet's display-default tokens (ETH and STRK) only. An account funded only in native mainnet USDC before deployment has no ETH or STRK, so it reads as empty and is skipped, and a real recoverable account is invisible to import.

Evidence

• Source: discoverRecoveryAccounts in apps/extension/src/background/onboarding/onboarding-ops.ts built its probe list from defaultWalletPreferences().tokens, i.e. the display defaults (ETH, STRK).
• Local behavioral check: the updated integration test in tests/background/onboarding/recovery-discovery.test.ts reports a USDC-only account as funded with the widened probe set, and the same test fails when only the probe line is reverted to the display-default implementation. The gap is real and the test is not vacuous.
• Native USDC contract and decimals match the wallet's curated registry entry (packages/features/portfolio/src/tokens/token-registry.ts): 0x033068f6539f8e6e6b131e6b2b814e6c34a5224bc66947c47dab9dfee93b35fb, 6 decimals.

Acceptance criteria

• The recovery scan probes a discovery-only token set that is a superset of the display defaults and includes native mainnet USDC; the user's displayed/tracked token set is unchanged.
• An undeployed account funded only in native USDC is reported funded and offered for import.
• Unit coverage: the probe set is a superset of the display defaults, native USDC is not a display default, and the scan probes the widened set.

Tracking

Incoming contribution #562 adds a discovery-only RECOVERY_PROBE_TOKENS set (the display defaults plus native mainnet USDC) and probes it in the recovery scan instead of the display-default tokens.

Limitation

The contributor's live-mainnet vendor-dataset scorecard was not independently reproduced; the check above is a local behavioral test.

Classification note: this repository has no feature label, so this enhancement is labelled enhancement (with phase:7, matching the surrounding import/recovery work).