refactor: standardize level names across all roles (#195 phase 1)

Rename levels to use consistent industry-standard terminology:
- dev: medior → mid
- qa: reviewer → mid, tester → junior, add senior level
- architect: opus → senior, sonnet → junior

Add backward-compatible migration for projects.json and openclaw.json
config via level aliases in selectors and projects parser.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/setup/config.ts

@@ -6,7 +6,7 @@
 import type { OpenClawPluginApi } from "openclaw/plugin-sdk";
 import { HEARTBEAT_DEFAULTS } from "../services/heartbeat.js";
 
-type ModelConfig = { dev: Record<string, string>; qa: Record<string, string> };
+type ModelConfig = { dev: Record<string, string>; qa: Record<string, string>; architect: Record<string, string> };
 
 /**
  * Write DevClaw model level config to openclaw.json plugins section.