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/bootstrap-hook.ts

@@ -17,8 +17,8 @@ import { getSessionKeyRolePattern } from "./roles/index.js";
  *
  * Session key format: `agent:{agentId}:subagent:{projectName}-{role}-{level}`
  * Examples:
- *   - `agent:devclaw:subagent:my-project-dev-medior` → { projectName: "my-project", role: "dev" }
- *   - `agent:devclaw:subagent:webapp-qa-reviewer`    → { projectName: "webapp", role: "qa" }
+ *   - `agent:devclaw:subagent:my-project-dev-mid`   → { projectName: "my-project", role: "dev" }
+ *   - `agent:devclaw:subagent:webapp-qa-mid`        → { projectName: "webapp", role: "qa" }
  *
  * Note: projectName may contain hyphens, so we match role from the end.
  */