restartGatewayProcessWithFreshPid() checks SUPERVISOR_HINT_ENV_VARS to
decide whether to let the supervisor handle the restart (mode=supervised)
or to fork a detached child (mode=spawned). The existing list only had
native launchd vars (LAUNCH_JOB_LABEL, LAUNCH_JOB_NAME) and systemd vars
(INVOCATION_ID, SYSTEMD_EXEC_PID, JOURNAL_STREAM).

macOS launchd does NOT automatically inject LAUNCH_JOB_LABEL into the
child environment. OpenClaw's own plist generator (buildServiceEnvironment
in service-env.ts) sets OPENCLAW_LAUNCHD_LABEL instead. So on stock macOS
LaunchAgent installs, isLikelySupervisedProcess() returned false, causing
the gateway to fork a detached child on SIGUSR1 restart. The original
process then exits, launchd sees its child died, respawns a new instance
which finds the orphan holding the port — infinite crash loop.

Fix: add OPENCLAW_LAUNCHD_LABEL, OPENCLAW_SYSTEMD_UNIT, and
OPENCLAW_SERVICE_MARKER to the supervisor hint list. These are set by
OpenClaw's own service environment builders for both launchd and systemd
and are the reliable supervised-mode signals.

Fixes openclaw#27605

(cherry picked from commit 792ce7b)