Tooling · Inspection: inspector, FPS meter, render counter and event logger

install_inspector draws gpui's debug inspector in Ely's look: a panel
with the picked box's source, ids and box model, and its margin,
border, padding and size drawn over the page through raise, since the
panel scrolls. FpsMeter counts frames on the executor's clock and
colors each by the frames it missed. RenderCounter counts the renders
of the view that draws it. EventLogger lists the input that reaches
what it holds, its canvas laid first so a child's stop hides nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tasks/ch31-43.md

@@ -359,10 +359,10 @@
 
 ## T43b Tooling · Inspection
 
-- [ ] InspectorOverlay
-- [ ] FPSMeter / PerfOverlay
-- [ ] RenderCounter
-- [ ] EventLogger
+- [x] InspectorOverlay → `tooling::install_inspector`: gpui's inspector, debug builds only, drawn by Ely: hover picks a box, the wheel steps out, a press holds; the box's margin, border, padding and size over the page, its model, source and ids in the panel
+- [x] FPSMeter / PerfOverlay → `tooling::FpsMeter`: frames per second over the last second, the worst frame, a bar per frame against the 60 Hz budget
+- [x] RenderCounter → `tooling::RenderCounter`: how often the view that draws it has rendered
+- [x] EventLogger → `tooling::EventLogger`: the input events that reach what it holds, newest first, moves run together, each timed from the first
 
 ## T43c Tooling · Catalogs