Two sync hot paths were stalling the dashboard event loop on a periodic
timer:
1. `pgrep -f vitest` ran via `execSync` in `getVitestProcessIds`
(`/api/system-stats`, `/api/kill-vitest`) and `killVitestProcesses`
(TUI memory-pressure check). On a busy machine pgrep walking the
process table can take 100ms+; execSync blocks the entire Node event
loop for that duration, so every concurrent dashboard request hangs
while pgrep runs. The TUI variant fired on every memory-pressure tick
(~2s when over threshold), the dashboard variant fired on every
system-stats poll (5s while the modal is open). Both now use execFile
with a callback wrapped in a Promise.
2. `discoverDashboardPiExtensions` (called from 3 /api/settings/pi-
extensions routes) did 6+ blocking existsSync/readFileSync calls per
invocation across legacy and fusion settings paths. Converted to
fs.promises.readFile/access and parallelized via Promise.all.
Behavior preserved:
- TUI memory-pressure detection still works (sync os.totalmem path
unchanged); auto-kill still fires on threshold breach.
- The `lastAutoKillAt` 30s re-fire gate is set before the async kill
starts, so concurrent ticks can't trigger duplicate kills.
- system-stats still polls every 5s while the modal is open and still
returns vitestProcessCount.
- All 7 system-stats / kill-vitest tests pass; all 6 settings/pi-
extensions tests pass. Test mocks updated for the (err, stdout, stderr)
callback signature.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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