refactor: replace inline HERMES_HOME re-implementations with get_hermes_home()

16 callsites across 14 files were re-deriving the hermes home path
via os.environ.get('HERMES_HOME', ...) instead of using the canonical
get_hermes_home() from hermes_constants. This breaks profiles — each
profile has its own HERMES_HOME, and the inline fallback defaults to
~/.hermes regardless.

Fixed by importing and calling get_hermes_home() at each site. For
files already inside the hermes process (agent/, hermes_cli/, tools/,
gateway/, plugins/), this is always safe. Files that run outside the
process context (mcp_serve.py, mcp_oauth.py) already had correct
try/except ImportError fallbacks and were left alone.

Skipped: hermes_constants.py (IS the implementation), env_loader.py
(bootstrap), profiles.py (intentionally manipulates the env var),
standalone scripts (optional-skills/, skills/), and tests.

plugins/memory/hindsight/__init__.py

@@ -290,8 +290,7 @@ class HindsightMemoryProvider(MemoryProvider):
         if self._mode == "local":
             def _start_daemon():
                 import traceback
-                from pathlib import Path
-                log_dir = Path(os.environ.get("HERMES_HOME", os.path.expanduser("~/.hermes"))) / "logs"
+                log_dir = get_hermes_home() / "logs"
                 log_dir.mkdir(parents=True, exist_ok=True)
                 log_path = log_dir / "hindsight-embed.log"
                 try:

plugins/memory/retaindb/__init__.py

@@ -504,7 +504,8 @@ class RetainDBMemoryProvider(MemoryProvider):
         self._user_id = kwargs.get("user_id", "default") or "default"
         self._agent_id = kwargs.get("agent_id", "hermes") or "hermes"
 
-        hermes_home_path = Path(os.environ.get("HERMES_HOME", Path.home() / ".hermes"))
+        from hermes_constants import get_hermes_home
+        hermes_home_path = get_hermes_home()
         db_path = hermes_home_path / "retaindb_queue.db"
         self._queue = _WriteQueue(self._client, db_path)