Adds two dev-only counters that attribute re-renders and store
notifications during an interaction, so a perf claim can be answered with
a number instead of a hunch:
window.__RENDER_COUNTS__ what re-rendered, and why (props/state/parent)
window.__ATOM_CHURN__ which store published it, and whether it mattered
The `wasted` column in each is the fix list — components that re-rendered
with no changed input, and stores that published a value equal to the
last one. Both are inert until start(), so idle cost is one branch per
commit and per notify.
React 19.2 removed injectProfilingHooks from react-dom, so the mark*
profiling family is unavailable and onCommitFiberRoot is the only channel
left. <Profiler> can't answer the question either: React invokes onRender
for every Profiler in a committed tree including subtrees that bailed
out, and a bailed-out subtree still reports nonzero actualDuration. This
uses bippy's didFiberRender instead. bippy over react-scan because
react-scan/lite is a thin wrapper over it while the package pulls ~217
transitive deps and floats two on latest.
main.tsx imports the entry statically above react-dom because react-dom
captures the devtools hook at module init — a late install reports
renderers=0 and observes zero commits. Production exclusion is handled by
a build-time alias to a no-op module rather than tree-shaking, since a
static side-effect import can't be eliminated.
Brooklyn Nicholson