fix(commands+CONTRACT): correct set.mode mode list

- src/commands/index.js: description now lists the actual schema modes
  (`optimalControl`, `priorityControl`, `maintenance`); was generic
  "auto / manual" which never matched the schema.
- CONTRACT.md: same fix — old list included `dynamiccontrol` (doesn't
  exist) and used lowercase names that don't match the canonical
  schema enum.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/commands/index.js

@@ -12,7 +12,7 @@ module.exports = [
     topic: 'set.mode',
     aliases: ['setMode'],
     payloadSchema: { type: 'string' },
-    description: 'Switch the machine group between auto / manual modes.',
+    description: 'Switch the operating mode. Allowed: `optimalControl`, `priorityControl`, `maintenance` (schema-validated in `machineGroupControl.json` → `mode.current`).',
     handler: handlers.setMode,
   },
   {