fix(security): redact secrets from execute_code sandbox output

* fix: root-level provider in config.yaml no longer overrides model.provider

load_cli_config() had a priority inversion: a stale root-level
'provider' key in config.yaml would OVERRIDE the canonical
'model.provider' set by 'hermes model'. The gateway reads
model.provider directly from YAML and worked correctly, but
'hermes chat -q' and the interactive CLI went through the merge
logic and picked up the stale root-level key.

Fix: root-level provider/base_url are now only used as a fallback
when model.provider/model.base_url is not set (never as an override).

Also added _normalize_root_model_keys() to config.py load_config()
and save_config() — migrates root-level provider/base_url into the
model section and removes the root-level keys permanently.

Reported by (≧▽≦) in Discord: opencode-go provider persisted as a
root-level key and overrode the correct model.provider=openrouter,
causing 401 errors.

* fix(security): redact secrets from execute_code sandbox output

The execute_code sandbox stripped env vars with secret-like names from
the child process (preventing os.environ access), but scripts could
still read secrets from disk (e.g. open('~/.hermes/.env')) and print
them to stdout. The raw values entered the model context unredacted.

terminal_tool and file_tools already applied redact_sensitive_text()
to their output — execute_code was the only tool that skipped this
step. Now the same redaction runs on both stdout and stderr after
ANSI stripping.

Reported via Discord (not filed on GitHub to avoid public disclosure
of the reproduction steps).

tools/code_execution_tool.py

@@ -596,6 +596,14 @@ def execute_code(
         stdout_text = strip_ansi(stdout_text)
         stderr_text = strip_ansi(stderr_text)
 
+        # Redact secrets (API keys, tokens, etc.) from sandbox output.
+        # The sandbox env-var filter (lines 434-454) blocks os.environ access,
+        # but scripts can still read secrets from disk (e.g. open('~/.hermes/.env')).
+        # This ensures leaked secrets never enter the model context.
+        from agent.redact import redact_sensitive_text
+        stdout_text = redact_sensitive_text(stdout_text)
+        stderr_text = redact_sensitive_text(stderr_text)
+
         # Build response
         result: Dict[str, Any] = {
             "status": status,