fix(tui_gateway): guard env var parsing against invalid values at import

_SLASH_WORKER_TIMEOUT_S and _pool used raw float()/int() on env vars
at module level. A non-numeric value (e.g. HERMES_TUI_SLASH_TIMEOUT_S=abc)
raises ValueError during import, preventing TUI gateway from starting
with no useful error message.

Wrap both parses in try/except with safe fallbacks:
- HERMES_TUI_SLASH_TIMEOUT_S: fallback to 45.0s
- HERMES_TUI_RPC_POOL_WORKERS: fallback to 4 workers

tui_gateway/server.py

@@ -125,9 +125,11 @@ _cfg_lock = threading.Lock()
 _cfg_cache: dict | None = None
 _cfg_mtime: float | None = None
 _cfg_path = None
-_SLASH_WORKER_TIMEOUT_S = max(
-    5.0, float(os.environ.get("HERMES_TUI_SLASH_TIMEOUT_S", "45") or 45)
-)
+try:
+    _slash_timeout = float(os.environ.get("HERMES_TUI_SLASH_TIMEOUT_S") or "45")
+except (ValueError, TypeError):
+    _slash_timeout = 45.0
+_SLASH_WORKER_TIMEOUT_S = max(5.0, _slash_timeout)
 _DETAIL_SECTION_NAMES = ("thinking", "tools", "subagents", "activity")
 _DETAIL_MODES = frozenset({"hidden", "collapsed", "expanded"})
 
@@ -153,8 +155,12 @@ _LONG_HANDLERS = frozenset(
     }
 )
 
+try:
+    _rpc_pool_workers = max(2, int(os.environ.get("HERMES_TUI_RPC_POOL_WORKERS") or "4"))
+except (ValueError, TypeError):
+    _rpc_pool_workers = 4
 _pool = concurrent.futures.ThreadPoolExecutor(
-    max_workers=max(2, int(os.environ.get("HERMES_TUI_RPC_POOL_WORKERS", "4") or 4)),
+    max_workers=_rpc_pool_workers,
     thread_name_prefix="tui-rpc",
 )
 atexit.register(lambda: _pool.shutdown(wait=False, cancel_futures=True))