feat(plugins): add enable/disable commands + interactive toggle UI (#3747)

Adds plugin management with three interfaces:

  hermes plugins          # interactive curses checklist (like hermes tools)
  hermes plugins enable   # non-interactive enable
  hermes plugins disable  # non-interactive disable
  hermes plugins list     # table with status column

Disabled plugins are stored in config.yaml under plugins.disabled and
skipped during discovery. Uses the same curses_checklist component as
hermes tools for the interactive UI.

Changes:
- hermes_cli/plugins.py: _get_disabled_plugins() + skip disabled during
  discover_and_load()
- hermes_cli/plugins_cmd.py: cmd_toggle() interactive UI, cmd_enable(),
  cmd_disable(), updated cmd_list() with status column
- hermes_cli/main.py: enable/disable subparser entries
- website/docs/reference/cli-commands.md: updated plugins section
- website/docs/user-guide/features/plugins.md: updated managing section

hermes_cli/plugins.py

@@ -68,6 +68,17 @@ def _env_enabled(name: str) -> bool:
     return os.getenv(name, "").strip().lower() in {"1", "true", "yes", "on"}
 
 
+def _get_disabled_plugins() -> set:
+    """Read the disabled plugins list from config.yaml."""
+    try:
+        from hermes_cli.config import load_config
+        config = load_config()
+        disabled = config.get("plugins", {}).get("disabled", [])
+        return set(disabled) if isinstance(disabled, list) else set()
+    except Exception:
+        return set()
+
+
 # ---------------------------------------------------------------------------
 # Data classes
 # ---------------------------------------------------------------------------
@@ -199,8 +210,15 @@ class PluginManager:
         # 3. Pip / entry-point plugins
         manifests.extend(self._scan_entry_points())
 
-        # Load each manifest
+        # Load each manifest (skip user-disabled plugins)
+        disabled = _get_disabled_plugins()
         for manifest in manifests:
+            if manifest.name in disabled:
+                loaded = LoadedPlugin(manifest=manifest, enabled=False)
+                loaded.error = "disabled via config"
+                self._plugins[manifest.name] = loaded
+                logger.debug("Skipping disabled plugin '%s'", manifest.name)
+                continue
             self._load_plugin(manifest)
 
         if manifests: