fix(batch): use max() for Stateful field in category combination

[NadavLevi]

When combining API categories for batch requests, the Stateful field was incorrectly using addition. This caused batches with 2+ stateful methods to have Stateful > 1, which failed the equality check (== CONSISTENCY_SELECT_ALL_PROVIDERS) and incorrectly used Quorum selection instead of BestResult.

Changed from addition to max() so any batch containing at least one stateful method is correctly treated as stateful (BestResult selection).

Before (bug):

• 2 stateful methods: 1+1=2, != 1, uses Quorum (wrong)

After (fix):

• 2 stateful methods: max(1,1)=1, == 1, uses BestResult (correct)

Description

Closes: #XXXX

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Author Checklist

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• read the contribution guide
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• confirmed the correct type prefix in the PR title
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• reviewed state machine logic, API design and naming, documentation is accurate, tests and test coverage

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Flag	Coverage Δ
consensus	8.55% <100.00%> (+<0.01%)	⬆️
protocol	33.87% <ø> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
x/spec/types/api_collection.go	8.60% <100.00%> (+8.60%)	⬆️

... and 2 files with indirect coverage changes

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[github-actions]

Test Results

    7 files  ± 0     85 suites  ±0   31m 20s ⏱️ -26s
3 334 tests +14  3 333 ✅ +14  1 💤 ±0  0 ❌ ±0 
3 527 runs  +14  3 526 ✅ +14  1 💤 ±0  0 ❌ ±0 

Results for commit 7fe44ad. ± Comparison against base commit e4f7444.