fix(gateway): detect stopped processes and release stale locks on --replace

[ygd58]

Fixes #2178

Root Cause

Two bugs when hermes gateway run --replace encounters a STOPPED (Ctrl+Z) process:

1. acquire_scoped_lock() treated stopped processes as alive — os.kill(pid, 0) succeeds for stopped processes, so stale lock files were never cleaned up
2. start_gateway() with --replace removed the PID file but not the scoped lock files in ~/.local/state/hermes/gateway-locks/

Fix (Option C: both fixes)

gateway/status.py — Option B:

• After os.kill(pid, 0) succeeds, check /proc/<pid>/status for process state
• If state is T (stopped) or t (tracing stop), treat as stale and clean up the lock

gateway/status.py — Option A:

• Added release_all_scoped_locks() function that removes all lock files in the lock directory

gateway/run.py:

• After remove_pid_file() in --replace logic, call release_all_scoped_locks() to clean up stale locks from the old gateway

[teknium1]

Merged via PR #2406. Cherry-picked with authorship preserved. Thanks!