Changes between 0.4.0-alpha.3 and v1.0.0.0: Null values changed to '' and 24h time values to 12h time values

### Command that triggered the bug

apiops publish

### Expected behavior

The extracted values are fine but after publish the values are changes:
Example:
Source JSON:
"firstSeen": "2026-07-11T14:01:26.0000000+00:00",
"lastSeen": "2026-07-11T14:58:54.0000000+00:00",
"zone": null,
Published values:
"firstSeen": "2026-07-11T02:01:26.0000000+00:00",
"lastSeen": "2026-07-11T02:58:54.0000000+00:00",
"zone": '',

### Actual behavior

Null values get replaced with empty string '' and 24h time values are replaced with 12h format values with no AM/PM flag.

### apiops CLI version

1.0.0.0

### Environment details

command runs in a gitlab pipeline on self hosted gitlab runner image: mcr.microsoft.com/dotnet/sdk:6.0
Nodejs version node-v22.14.0-linux-x64

### CI/CD environment

Other

### Is this bug blocking you?

Yes

Start by reproducing `apiops publish` with the source JSON and environment details from the issue, then trace the publish path that serializes extracted values. Done means published output preserves null values and the original 24-hour time values; add or update a regression test for both cases.

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