perf(tui): avoid importing classic CLI during tool discovery

TUI session readiness was still laggy after the gateway-ready fixes. Profiling
session.create -> session.info showed the slow phase is background AIAgent
construction (~1.1s). A cProfile run of tui_gateway.server::_make_agent showed
model_tools/tool discovery importing tools.code_execution_tool, whose
module-level EXECUTE_CODE_SCHEMA calls _get_execution_mode(), which imported
cli.CLI_CONFIG.

That pulled the classic interactive CLI stack (prompt_toolkit/Rich and REPL
setup) into every agent startup path, including hermes --tui where it is not
used. Replace that with hermes_cli.config.read_raw_config(), which is cached and
reads only the raw code_execution section. Existing defaults still apply when
the key is absent.

Measurements on macOS Terminal.app:
- import run_agent: ~466ms -> ~347ms
- model_tools import: ~418ms -> ~272ms
- _make_agent: ~1452ms -> ~1239ms
- session.create -> session.info: ~1167ms -> ~999ms
- full hermes --tui ready p50: ~1655ms -> ~1537ms

Tests:
- scripts/run_tests.sh tests/tools/test_code_execution_modes.py tests/tools/test_code_execution.py

tools/code_execution_tool.py

@@ -1309,10 +1309,20 @@ def _kill_process_group(proc, escalate: bool = False):
 
 
 def _load_config() -> dict:
-    """Load code_execution config from CLI_CONFIG if available."""
+    """Load code_execution config without importing the interactive CLI.
+
+    This helper is called while building the module-level execute_code schema
+    during tool discovery.  Importing ``cli`` here pulls prompt_toolkit/Rich and
+    a large chunk of the classic REPL onto every agent startup path, including
+    ``hermes --tui`` where it is never used.  Read the lightweight raw config
+    instead; the config layer already caches by (mtime, size), and an absent
+    key cleanly falls back to DEFAULT_EXECUTION_MODE.
+    """
     try:
-        from cli import CLI_CONFIG
-        return CLI_CONFIG.get("code_execution", {})
+        from hermes_cli.config import read_raw_config
+
+        cfg = read_raw_config().get("code_execution", {})
+        return cfg if isinstance(cfg, dict) else {}
     except Exception:
         return {}