[Feature]: Surface reducer execution time in performance panel

[omoladeodetara]

Problem Statement

The meta-reducer already measures reducer execution time via performanceTracker.measureRenderTime(), but the value is passed into a callback and then discarded it is never included in the STATE_CHANGE WebSocket message and never shown in the performance panel.

The performance panel currently only shows Angular render time (via afterNextRender), so users cannot distinguish between a slow reducer and slow change detection/DOM rendering.

Proposed Solution

Include reducer execution time in the STATE_CHANGE message and display it alongside render time in the performance panel.

Changes required:

• meta-reducer.ts: capture the reducer duration and add it to StateChangeMessage as reducerTime?: number
• core.models.ts: add reducerTime?: number to the StateChangeMessage interface
• performance-panel.component.ts: read reducerTime from incoming messages and include it in RenderEntry
• performance-panel.component.html: add a Reducer Time column to the slowest renders table; update the summary cards

Alternatives Considered

Measuring reducer time in the UI by diffing timestamps not accurate enough given network/serialization latency.

Component

Performance Panel (ngrx-devtool-ui) + Core Library (ngrx-devtool)