fix(gateway): use portable ps scan for gateway PIDs

[iuyua9]

Summary:

• avoid Linux-specific ps eww flags when scanning gateway processes on non-Windows systems
• use ps aux directly on macOS, where the BSD ps output shape is stable for this scan
• keep structured ps -A ww -o pid=,command= on other POSIX systems and fall back to ps aux when that output is empty
• add regression coverage for macOS command selection and the POSIX fallback path

Why:

• find_gateway_pids() backs hermes gateway status and update/restart flows
• if the process-table scan returns empty on macOS, Hermes can report that a manual gateway is not running even when it is
• this keeps PID-file detection intact and only hardens the supplemental process scan

Tests:

• python3 -m pytest tests/hermes_cli/test_gateway.py -q
• git diff --check

Related:

• Follows the same macOS failure mode described in fix(gateway): find_gateway_pids works on macOS #10684; that PR was closed without merging and current main still contains the incompatible ps -A eww scan.

[teknium1]

Closing in favor of #22860 (salvage of #22693 by @wesleysimplicio). #22693 addresses a more severe failure mode — slim Docker images that ship without procps at all (no ps binary), which is the dominant production deployment surface. Your /proc-less macOS BSD ps flag matrix targets a different failure mode (#10684) which is complementary and can layer on top in a follow-up — your ps aux matrix would replace the still-broken ps -A eww fallback that #22693 keeps in its no-/proc branch. Thanks for the contribution!