FEE_VERSION2 reuses fee_version_number 1 and is missing from FEE_VERSIONS #4647

Summary

FEE_VERSION2 (packages/rs-platform-version/src/version/fee/v2.rs) declares fee_version_number: 1, the same number as FEE_VERSION1, and is absent from FEE_VERSIONS (fee/mod.rs). FeeVersion::get(1) therefore always returns FEE_VERSION1, even for epochs that ran on FEE_VERSION2 (protocol v9 and later).

Why it matters

Only the fee version number is persisted for previous epochs:

• PlatformStateForSavingV1 stores previous_fee_versions as epoch index -> fee_version_number (aux storage, rehydrated on every restart).
• ReducedPlatformStateV0 (state sync, feat(drive-abci): state sync via ABCI snapshots with reduced platform state (protocol v15) #4520) stores the same map in the replicated Misc tree and rehydrates it on a state-synced node.

Both round trips silently substitute FEE_VERSION1 for FEE_VERSION2. It is latent today only because the two schedules have identical storage fees, and previous_fee_versions is consulted solely to price storage refunds (rs-drive/src/fees/op.rs). The first FeeVersion that changes a storage or processing fee without taking a distinct number turns this into a consensus fork between nodes that restarted (or state-synced) and nodes that did not.

Fix

Give FEE_VERSION2 its own number (2) and add it to FEE_VERSIONS at index 1. That changes what a restarted or state-synced node computes for old epochs, so it is protocol-visible and needs a versioned migration rather than an in-place edit.

The #[ignore]d test fee_version_numbers_are_unique_and_resolvable in fee/mod.rs pins the defect; un-ignore it with the fix.

Rule going forward

Every FeeVersion constant needs a unique fee_version_number and an entry in FEE_VERSIONS at the index that number implies.