fix(cli): respect HERMES_HOME in all remaining hardcoded ~/.hermes paths

Several files resolved paths via Path.home() / ".hermes" or
os.path.expanduser("~/.hermes/..."), bypassing the HERMES_HOME
environment variable. This broke isolation when running multiple
Hermes instances with distinct HERMES_HOME directories.

Replace all hardcoded paths with calls to get_hermes_home() from
hermes_cli.config, consistent with the rest of the codebase.

Files fixed:
- tools/process_registry.py (processes.json)
- gateway/pairing.py (pairing/)
- gateway/sticker_cache.py (sticker_cache.json)
- gateway/channel_directory.py (channel_directory.json, sessions.json)
- gateway/config.py (gateway.json, config.yaml, sessions_dir)
- gateway/mirror.py (sessions/)
- gateway/hooks.py (hooks/)
- gateway/platforms/base.py (image_cache/, audio_cache/, document_cache/)
- gateway/platforms/whatsapp.py (whatsapp/session)
- gateway/delivery.py (cron/output)
- agent/auxiliary_client.py (auth.json)
- agent/prompt_builder.py (SOUL.md)
- cli.py (config.yaml, images/, pastes/, history)
- run_agent.py (logs/)
- tools/environments/base.py (sandboxes/)
- tools/environments/modal.py (modal_snapshots.json)
- tools/environments/singularity.py (singularity_snapshots.json)
- tools/tts_tool.py (audio_cache)
- hermes_cli/status.py (cron/jobs.json, sessions.json)
- hermes_cli/gateway.py (logs/, whatsapp session)
- hermes_cli/main.py (whatsapp/session)

Tests updated to use HERMES_HOME env var instead of patching Path.home().

Closes #892

(cherry picked from commit 78ac1bba43)

tools/process_registry.py

@@ -47,11 +47,13 @@ from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, Dict, List, Optional
 
+from hermes_cli.config import get_hermes_home
+
 logger = logging.getLogger(__name__)
 
 
 # Checkpoint file for crash recovery (gateway only)
-CHECKPOINT_PATH = Path(os.path.expanduser("~/.hermes/processes.json"))
+CHECKPOINT_PATH = get_hermes_home() / "processes.json"
 
 # Limits
 MAX_OUTPUT_CHARS = 200_000      # 200KB rolling output buffer