### What problem does this PR solve?
Changed test priorities in multiple test files, downgrading from p1 to
p2 and p2 to p3.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
This PR adds missing web API tests (system, search, KB, LLM, plugin,
connector). It also addresses a contract mismatch that was causing test
failures: metadata updates did not persist new keys (update‑only
behavior).
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [x] Other (please describe): Test coverage expansion and test helper
instrumentation
