fix(spartan-bench): tolerate older node images in SlasherConfig schema (#23351)

## Summary

Fixes `block_capacity.test.ts` (nightly spartan bench) failing against a
stale nightly Aztec image.

The nightly-spartan-bench workflow checks out test code from
`merge-train/spartan` but runs against the prebuilt nightly Aztec docker
image, which is built from `next`. `merge-train/spartan` introduced two
new required fields on `SlasherConfigSchema`:

- `slashDataWithholdingToleranceSlots: z.number()` (PR #23116)
- `slashBroadcastedInvalidCheckpointProposalPenalty: schemas.BigInt`

The nightly image (built from `next`, which does not yet have these PRs)
does not include these fields in its config response. As a result the
very first call in the test — `updateSequencersConfig(config, {
minTxsPerBlock: 0 })` → `client.getConfig()` — fails Zod validation,
every subbench dies on `accountAddresses[0] === undefined` in
`beforeAll`, and `block_capacity.test.ts` reports 8/8 failures (see
<http://ci.aztec-labs.com/2679b1738ea39752>).

## Fix

Make the two new fields tolerate undefined in the response schema by
giving them sensible defaults (`3` and `0n`, matching
`spartan/environments/network-defaults.yml` and the slasher defaults).
The TypeScript `SlasherConfig` interface stays strict (output type is
unchanged); only the parse side becomes forgiving, matching the pattern
used by the other recently-added schema fields in `configs.ts`,
`p2p.ts`, and `validator.ts`.

`partial()` (used by `setConfig`) wraps each field with `.optional()` on
the outside, which bypasses `.default()` — so partial updates that omit
these fields will continue to omit them server-side rather than
accidentally clobbering existing values to the defaults.

## Test plan

- nightly-spartan-bench → block-capacity-benchmark passes against the
stale-image scenario
- existing `aztec-node-admin.test.ts` getConfig test continues to pass
(fields are present in the mock)


---
*Created by
[claudebox](https://claudebox.work/v2/sessions/5cbfb8fe5a58619c) ·
group: `slackbot`*

Author: AztecBot

yarn-project/stdlib/src/interfaces/slasher.ts

@@ -38,12 +38,16 @@ export const SlasherConfigSchema = zodFor<SlasherConfig>()(
     slashValidatorsAlways: z.array(schemas.EthAddress),
     slashValidatorsNever: z.array(schemas.EthAddress),
     slashDataWithholdingPenalty: schemas.BigInt,
-    slashDataWithholdingToleranceSlots: z.number(),
+    // Tolerated as undefined to allow validating responses from older node images that
+    // predate the per-slot data-withholding watcher (PR #23116).
+    slashDataWithholdingToleranceSlots: z.number().default(3),
     slashInactivityTargetPercentage: z.number(),
     slashInactivityConsecutiveEpochThreshold: z.number(),
     slashInactivityPenalty: schemas.BigInt,
     slashProposeInvalidAttestationsPenalty: schemas.BigInt,
-    slashBroadcastedInvalidCheckpointProposalPenalty: schemas.BigInt,
+    // Tolerated as undefined to allow validating responses from older node images that
+    // predate this slasher penalty being added.
+    slashBroadcastedInvalidCheckpointProposalPenalty: schemas.BigInt.default(0n),
     slashDuplicateProposalPenalty: schemas.BigInt,
     slashDuplicateAttestationPenalty: schemas.BigInt,
     slashAttestDescendantOfInvalidPenalty: schemas.BigInt,