### What problem does this PR solve?
Updates pre-existing HTTP API and SDK tests to align with current
backend behavior (validation errors, 404s, and schema defaults). This
ensures p3 regression coverage is accurate without changing production
code.
### Type of change
- [x] Other (please describe): align p3 HTTP/SDK tests with current
backend behavior
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Co-authored-by: Liu An <asiro@qq.com>