test(promql): enforce range step parity in production E2E

[zzylol]

Addresses #487 and is stacked on #505 because that branch supplies the canonical collector-free warm matrix used for the regression.

For every supported PromQL family, the production-process test now:

• asserts the exact requested range timestamps and step count;
• independently calls /api/v1/query at each requested timestamp;
• compares labels and values at each range step with the corresponding instant evaluation;
• retains warm provenance and no-fallback assertions.

This closes the detection gap that allowed native pane-close timestamps or ignored step_ms to pass.

Validation: cargo test -p data_plane --test asapquery_compatibility_process_e2e -- --nocapture (1 passed).

Intentionally left open and unmerged.