Bug: hermes doctor --fix does not auto-fix custom_providers structure

Description

hermes doctor correctly detects when custom_providers is a dict (old format) instead of a list (new format), but running hermes doctor --fix does not actually rewrite the config. The issue is reported every time, but the fix is never applied.

Steps to reproduce

1. Have a ~/.hermes/config.yaml with custom_providers as a dict:

   custom_providers:
     modelrelay:
       api: openai-completions
       base_url: http://op3:7352/v1

2. Run hermes doctor — it reports:

   ✗ custom_providers is a dict — it must be a YAML list (items prefixed with '-')

3. Run hermes doctor --fix — the same issue is still reported, nothing is fixed.

Root cause

In hermes_cli/doctor.py (lines 762-778), the validate_config_structure check reports config structure issues but has no should_fix branch. Compare with the stale root-level keys check (lines 746-756) which correctly handles should_fix by rewriting the config with atomic_yaml_write.

The relevant code block:

# Validate config structure (catches malformed custom_providers, etc.)
try:
    from hermes_cli.config import validate_config_structure
    config_issues = validate_config_structure()
    if config_issues:
        _section("Config Structure")
        for ci in config_issues:
            if ci.severity == "error":
                check_fail(ci.message)
            else:
                check_warn(ci.message)
            for hint_line in ci.hint.splitlines():
                check_info(hint_line)
            issues.append(ci.message)  # <-- always appended, never fixed
except Exception:
    pass

There is no if should_fix: block here, unlike every other check in the doctor (e.g. stale root keys at line 746, missing .env at line 508, missing config.yaml at line 695).

Expected behavior

When --fix is passed, the doctor should convert custom_providers from dict format to list format automatically, similar to how it already migrates stale root-level keys.

Suggested fix

Add a should_fix branch that transforms custom_providers from dict to list:

if should_fix:
    import yaml as _yaml
    config_path = HERMES_HOME / 'config.yaml'
    cfg = _yaml.safe_load(config_path.read_text(encoding="utf-8")) or {}
    cp = cfg.get("custom_providers")
    if isinstance(cp, dict):
        cfg["custom_providers"] = [
            {"name": k, **v} for k, v in cp.items()
        ]
        from utils import atomic_yaml_write
        atomic_yaml_write(config_path, cfg)
        check_ok("Converted custom_providers from dict to list format")
        fixed_count += 1

Environment

• hermes-agent version: latest (v23 config)
• Platform: Linux (WSL)