fix(ethereum): route GetWallet's wallet-ID fallback by scheme, not error type

[mswilkison]

Summary

Addresses a Codex finding (relayed via the #4119 review): TbtcChain.GetWallet derived a legacy wallet ID on any error from the canonical walletID accessor. For a FROST wallet on a canonical Bridge, a transient call failure would silently yield the left-padded legacy ID — and callers use WalletChainData.WalletID to choose P2TR (FROST) vs P2WPKH (legacy) scripts, so the node would build or search the wrong wallet script.

Why route by scheme (revised after Codex P1)

The first revision distinguished by error type (a sentinel for the missing accessor, surface everything else). Codex correctly flagged a P1 regression: a legacy on-chain Bridge built with the current generated binding still satisfies the accessor interface, so its missing walletID function returns a normal RPC/ABI error — not the sentinel — and that revision would surface it and break GetWallet on exactly the legacy deployments the fallback exists for. Error type cannot reliably separate "function absent on-chain" from "transient."

So this routes by scheme, using the wallet's EcdsaWalletID (which GetWallet already reads, and which the codebase already uses to infer scheme — zero ⇒ FROST):

• Legacy ECDSA wallet (EcdsaWalletID != 0): its canonical wallet ID equals its legacy derivation, so fall back on any accessor error — and it's the only option on a legacy Bridge lacking the accessor.
• FROST wallet (EcdsaWalletID == 0): requires the canonical ID; surface the error rather than return a wrong legacy ID. A FROST wallet only exists on a canonical-ID Bridge, so such an error is genuinely transient.

Logic is extracted into resolveWalletID(bridge, walletPublicKeyHash, ecdsaWalletID).

Tests

TestResolveWalletID covers all four cases: accessor success → canonical; FROST + accessor error → surfaced; legacy + accessor error → legacy fallback (the P1 regression guard — verified to fail if the routing surfaces errors for legacy wallets); legacy + missing-accessor binding → legacy fallback. gofmt + go vet clean; full pkg/chain/ethereum suite passes.

Found during the Codex review batch on #4115–#4120; revised per the Codex P1 re-review.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

🤖 Generated with Claude Code

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