fix(ui): clamp deltaTime to 1ms in pose-renderer FPS calc (#519 Bug 2) (#610)

When two render frames land in the same performance.now() tick,
`currentTime - lastFrameTime === 0`, so `fps = 1000 / 0 = Infinity`,
and `averageFps = averageFps * 0.9 + Infinity * 0.1 = Infinity` poisons
the EMA forever after a single zero-dt tick. The UI then displays
"Infinity FPS" until reload.

Floor deltaTime at 1 ms before the division. That caps displayed FPS at
1000 (far above any real render rate so the cap is never observed in
practice) but keeps the EMA finite.

Reported in #519 ("Bug 2 — FPS shows Infinity") by @kapilsoni2013 on a
3-node ESP32-S3-WROOM multi-node setup with edge-tier 1 + 2.

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- **`ui/utils/pose-renderer.js` no longer divides by zero** when two render frames land in the same `performance.now()` tick (issue #519 Bug 2). `deltaTime` is now `Math.max(currentTime - lastFrameTime, 1)` before the `1000 / deltaTime` division, capping displayed FPS at 1000 — far above any real render rate, but finite so the EMA `averageFps = averageFps * 0.9 + fps * 0.1` no longer poisons itself to `Infinity` on a single zero-dt tick.
+
 ### Removed
 - **Stub crates `wifi-densepose-api`, `wifi-densepose-db`, `wifi-densepose-config`** (closes #578).
   Each was a single-line doc-comment placeholder with an empty `[dependencies]`

ui/utils/pose-renderer.js

@@ -651,14 +651,18 @@ export class PoseRenderer {
     this.performanceMetrics.frameCount++;
 
     if (this.performanceMetrics.lastFrameTime > 0) {
-      const deltaTime = currentTime - this.performanceMetrics.lastFrameTime;
+      // Clamp to a minimum dt so consecutive frames within the same
+      // performance.now() tick don't yield Infinity (issue #519 Bug 2).
+      // 1 ms floor caps the displayed FPS at 1000 — far above any real
+      // render rate, but finite so the EMA stays well-defined.
+      const deltaTime = Math.max(currentTime - this.performanceMetrics.lastFrameTime, 1);
       const fps = 1000 / deltaTime;
-      
+
       // Update average FPS using exponential moving average
       if (this.performanceMetrics.averageFps === 0) {
         this.performanceMetrics.averageFps = fps;
       } else {
-        this.performanceMetrics.averageFps = 
+        this.performanceMetrics.averageFps =
           (this.performanceMetrics.averageFps * 0.9) + (fps * 0.1);
       }
     }