_loadVerified assembly offsets are still wrong on main (PR #37 fix was not applied)

This was fixed in PR #37 but the PR was closed without merging. The fix was never applied to main.

`src/CertManager.sol` lines 581-584 still have wrong offsets:

```solidity
ca := mload(add(packed, 0x1)) // should be 0x0
notAfter := mload(add(packed, 0x9)) // should be 0x1
maxPathLen := mload(add(packed, 0x11)) // should be 0x9
subjectHash := mload(add(packed, 0x31)) // should be 0x11
```

`abi.encodePacked` layout: ca(1) || notAfter(8) || maxPathLen(8) || subjectHash(32) || pubKey(48)

The warm cache path calls `_loadVerified` for every previously verified cert. With wrong offsets, cached certs return garbage values for ca, notAfter, maxPathLen and subjectHash. This affects the NitroValidator flow via `verifyCachedCertBundle`.

Fix diff in PR #37: https://github.com/base/nitro-validator/pull/37

Start in src/CertManager.sol at lines 581-584 and trace the verifyCachedCertBundle path that calls _loadVerified. Compare the mload offsets with the documented abi.encodePacked layout and the fix described in PR #37; done means cached certificates return the correct ca, notAfter, maxPathLen, and subjectHash values.

Written by the indexing model from the issue text.