Infer proven post-state balance/allowance deltas (replace event-only approval heuristic)

[Th0rgal]

Problem

Remaining token approvals is currently inferred from Approval events only. This is lossy:

• transfers/transferFrom can change allowance without emitting a new Approval event (common token behavior)
• event-only inference can over-report stale approvals
• users can see movement events that suggest spend happened while UI still warns allowance remains

Goal

Compute post-state token allowances and balance changes from simulation/replay state, and attach RPC proofs so the desktop verifier can validate those post-state claims offline.

Scope

1. Infer all touched token balances and allowance slots from simulation trace/replay context.
2. For each touched account/token slot, fetch post-state values at pinned block context and include proofs.
3. Extend evidence package with a postStateEffects artifact (or equivalent) containing:
   • native balances changed
   • ERC-20 balances changed
   • ERC-20 allowances changed (owner, spender, token, before, after)
   • proof material for each claimed slot/account
4. Verify these proofs in desktop/CLI against the same anchored state root.
5. Render approvals as actual post-state deltas (not event heuristic), and keep event-based display as fallback only.

Design constraints

• Keep chain anchor consistency: simulation/witness/proof must reference same block+state root.
• Preserve witness-only flow semantics.
• Do not rely on token event emission behavior for approval correctness.

Acceptance criteria

• For a tx where allowance is consumed without an Approval event, UI shows correct post-state allowance.
• For a tx where approval is revoked to zero, UI does not show it as remaining.
• Post-state effects fail closed when proofs are missing/invalid.
• Desktop and generator display the same approval/balance conclusions for the same package.
• Add regression tests covering:
  • no-approval-event allowance decrease
  • explicit revoke-to-zero
  • unchanged allowance
  • partial proof/missing proof failure paths

Related

• Current heuristic implementation: packages/core/src/lib/simulation/summary.ts (computeRemainingApprovals)
• Event decoder basis: packages/core/src/lib/simulation/event-decoder.ts