test(BeraChef): implement TODO fuzz and invariant tests for reward allocation

[sailorpepe]

Summary

BeraChef.t.sol has explicit TODOs for missing fuzz and invariant tests:

• Line 506: // TODO: Fuzz test — empty testFuzz_QueueANewRewardAllocation
• Line 509: // TODO: Invariant test — commented-out invariant test
• Line 352: Misleading TODO comment on test_FallbackToDefaultRAWhenLoweringMaxWeightPerVault

Additionally, Staking.t.sol has 3 vague // TODO: total supply is limited by PRECISION comments (lines 131, 149, 165) that don't explain the actual constraint.

Proposal

1. Implement testFuzz_QueueANewRewardAllocation — generates random valid weight distributions across 1-2 vaults, queues them, and verifies stored state
2. Add testFuzz_QueueActivateRewardAllocation_Invariants — exercises the full queue→activate→verify lifecycle with invariant checks
3. Fix the misleading TODO comment
4. Replace vague PRECISION TODOs with precise explanations of the rewardPerToken truncation boundary

I have a PR ready.