feat(steps): lay out screen pictures by region and render region captions

Adds region-based layout support for screens: steps now carry region information, and the server packs regions into dedicated bands with per-region captions. UI changes introduce RegionCaption and region-aware step rendering; StepsModel and related views (StepsView) consume region data, while the region-aware layout keeps anchor and region boundaries intact. Tests and docs updated to reflect region-driven organization and visualization of screen regions. This enables visualizing a screen’s picture as region-based columns rather than a single distance-driven row.

src/telemetry/index.ts

@@ -238,7 +238,7 @@ export class Telemetry {
     const day = this.utcDay();
     const cn = client?.name?.slice(0, 64);
     const cv = client?.version?.slice(0, 32);
-    const key = [day, kind, name, cn ?? '', cv ?? ''].join('');
+    const key = [day, kind, name, cn ?? '', cv ?? ''].join('\u0000');
     const line = this.counts.get(key);
     if (line) {
       line.c += 1;