fix: maxWithdraw returns 0 instead of reverting on zero share ratio

[thedavidmeister]

Summary

• ERC-4626 requires maxWithdraw MUST NOT revert.
• ERC20PriceOracleReceiptVault._shareRatioUserAgnostic returns id, so maxWithdraw(owner, 0) produces a zero share ratio and panics with Panic(0x12) inside _calculateRedeem. A zero share ratio means no deposit at this id has ever existed; the max withdrawable is 0. Short-circuit before the math.
• Pinned by a targeted test (testMaxWithdrawZeroIdDoesNotRevert) and a broad fuzz (testMaxWithdrawAnyIdDoesNotRevert).

Part of #303 (full ERC-4626 spec compliance is broader and remains open).

Test plan

• TDD: new tests fail against unfixed code with Panic(0x12); pass after the fix.
• Full non-fork suite green (341/341).
• CI passes

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 5e22987b-0e3c-4430-b56a-7f31e2a40513

📥 Commits

Reviewing files that changed from the base of the PR and between 78390b1 and b9c0957.

📒 Files selected for processing (3)

• src/abstract/ReceiptVault.sol
• test/src/concrete/authorize/OffchainAssetReceiptVaultPaymentMintAuthorizerV1.deposit.t.sol
• test/src/concrete/vault/ERC20PriceOracleReceiptVault.maxWithdraw.t.sol

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 2026-05-14-max-withdraw-no-revert

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