feat(perf): explicit toggle for live thread-group CPU polling (#891)

* feat(perf): explicit toggle for live thread-group CPU polling

Replace implicit thread-group collection (section open / pin) with a persisted
checkbox so Linux /proc scans run only when the user opts in for diagnosis.

Fix IPC: pass includeThreadGroups (camelCase) so Tauri maps the flag to Rust;
reset the CPU baseline when the option changes so thread % deltas are valid.

* docs: CHANGELOG and credits for PR #891

* fix(perf): gate CHILD_RESCAN_EVERY to Linux/macOS only

Avoid dead_code warning on Windows where perf child-PID rescan is unused.

src/components/sidebar/perfProbe/PerfLivePollControls.tsx

@@ -2,12 +2,15 @@ import {
   PERF_LIVE_POLL_MS_MAX,
   PERF_LIVE_POLL_MS_MIN,
   PERF_LIVE_POLL_MS_STEP,
+  setPerfLiveIncludeThreadGroups,
   setPerfLivePollIntervalMs,
+  usePerfLiveIncludeThreadGroups,
   usePerfLivePollIntervalMs,
 } from '../../../utils/perf/perfLivePollSettings';
 
 export default function PerfLivePollControls() {
   const pollMs = usePerfLivePollIntervalMs();
+  const includeThreadGroups = usePerfLiveIncludeThreadGroups();
   const pollSec = (pollMs / 1000).toFixed(1);
 
   return (
@@ -28,6 +31,19 @@ export default function PerfLivePollControls() {
           onChange={e => setPerfLivePollIntervalMs(Number(e.target.value))}
         />
       </label>
+      <label className="perf-live-poll__row perf-live-poll__row--check">
+        <input
+          type="checkbox"
+          checked={includeThreadGroups}
+          onChange={e => setPerfLiveIncludeThreadGroups(e.target.checked)}
+        />
+        <span className="perf-live-poll__check-label">
+          CPU by psysonic threads
+        </span>
+      </label>
+      <p className="perf-live-poll__hint">
+        Scans in-process thread groups each poll (Linux). Off by default — enable only while diagnosing.
+      </p>
     </section>
   );
 }