## Why

Steps 1-3 addressed the root causes of local controlled-player jitter: replay granularity (one-shot → fixed substeps), prediction cadence (Time.fixedDeltaTime → server cadence), and send interval oscillation (sign-toggle → dead-band hysteresis). Step 4 is a measurement and evaluation step to determine whether those fixes resolved the jitter or if further local visual correction refinement is warranted.

## What Changes

This is a validation step, not a code change. The artifacts confirm the acceptance criteria through manual testing and diagnostics observation:

- Run loopback test with steady turn-and-move input.
- Observe correction magnitude diagnostics from MainUI (校正：pos差=X rot差=Y°) to verify corrections are small.
- Observe acknowledged move tick to confirm input pipeline is healthy.
- Do NOT modify remote player interpolation or introduce new local smoothing.
- If jitter persists at meaningful magnitude after Steps 1-3, document residual error for Step 5 (regression coverage).

## Capabilities

### New Capabilities
- (none — this is a measurement/validation step with no new spec requirements)

### Modified Capabilities
- (none)

## Impact

No code changes. This step validates whether Steps 1-3 achieved the acceptance criteria or whether additional local visual correction refinement is needed.