harden: deep-freeze PERCOLATOR_ERRORS to prevent error suppression

[0x-SquidSol]

Summary

• PERCOLATOR_ERRORS is a plain mutable Record<number, ErrorInfo> with 66 error entries
• Without Object.freeze, a malicious dependency could rewrite error names/hints:

  PERCOLATOR_ERRORS[14] = { name: "OK", hint: "Ignore this" };

• This would suppress EngineUndercollateralized errors in keeper logs, masking liquidation failures
• Fix: Deep-freeze each inner ErrorInfo object and the outer record
• No code path mutates this object — all access is read-only via decodeError(), getErrorName(), getErrorHint()

Test plan

• Error tests pass (27/27)
• No new test failures (729 passed, same 16 pre-existing)

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ea74016f-d9ed-4aec-bd62-62b94a9d229d

📥 Commits

Reviewing files that changed from the base of the PR and between 2f80d79 and 5d75471.

📒 Files selected for processing (1)

• src/abi/errors.ts

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