Output: expand verbose render progress

README.md

@@ -236,7 +236,12 @@ path automatically.
 
 The PSF-cache completion line is printed before tracing and catalog splatting
 begin.  For long renders, pass `--verbose` to print catalog-prefetch state,
-splat and image-write boundaries without adding work to the splat hot path.
+splat-worker local heartbeats (8, 16, 32, ... completed triangles per worker),
+and image-write boundaries.  The worker heartbeats use neither global progress
+accounting nor cross-worker synchronization.
+Verbose ray-trace output reports the initial mesh trace and refinement stages
+for single frames; movie mode additionally reports each generation's sample
+count and each time slab's activation and terminal-ray summary.
 Movie renders always print one summary per time slab; `--verbose` also prints
 the ray counts before each slab is loaded.