The branch was missing the ProcessManager null-pid hotfix that landed on
main (cb4d12d9); a straight cherry-pick conflicted because Rector had
already reshaped the bodies here (the `(int) $pid` casts were removed).
Re-apply the fix branch-adapted: make all nine /proc pid checks accept
`?int $pid` (isRunning, isNamedProcessRunning, isStreamRunning,
producerKind, resourceSample, kill, getProcessAge, isStreamAlive,
isMonitorAlive) plus `?string $exe`. No cast is needed — each guard is
`$pid <= 0`/`<= 1` and `null <= 0` is true in PHP, so null returns the
safe "not running" result before reaching any /proc access. Docblocks
corrected to `int|null` so a future cs-fix run does not re-narrow.
Also fix Database::escape(string $string) -> ?string with a `(string)`
cast: PDO::quote is strict on PHP 8.1 and callers pass null.
Add TYPE_AUDIT.md tracking the remaining cs-fix null-crash surface
(~237 files) and the per-file hardening process. 726 tests green.
