feat: Implement Architect role & design_task tool (#189)

Adds the Architect role for design/architecture investigations with
persistent sessions and structured design proposals.

## New Features

- **Architect role** with opus (complex) and sonnet (standard) levels
- **design_task tool** — Creates To Design issues and dispatches architect
- **Workflow states:** To Design → Designing → Planning
- **Completion rules:** architect:done → Planning, architect:blocked → Refining
- **Auto-level selection** based on complexity keywords

## Files Changed (22 files, 546 additions)

### New Files
- lib/tools/design-task.ts — design_task tool implementation
- lib/tools/design-task.test.ts — 16 tests for architect functionality

### Core Changes
- lib/tiers.ts — ARCHITECT_LEVELS, WorkerRole type, models, emoji
- lib/workflow.ts — toDesign/designing states, completion rules
- lib/projects.ts — architect WorkerState on Project type
- lib/dispatch.ts — architect role support in dispatch pipeline
- lib/services/pipeline.ts — architect completion rules
- lib/model-selector.ts — architect level selection heuristic

### Integration
- index.ts — Register design_task tool, architect config schema
- lib/notify.ts — architect role in notifications
- lib/bootstrap-hook.ts — architect session key parsing
- lib/services/tick.ts — architect in queue processing
- lib/services/heartbeat.ts — architect in health checks
- lib/tools/health.ts — architect in health scans
- lib/tools/status.ts — architect in status dashboard
- lib/tools/work-start.ts — architect role option
- lib/tools/work-finish.ts — architect validation
- lib/tools/project-register.ts — architect labels + role scaffolding
- lib/templates.ts — architect instructions + AGENTS.md updates
- lib/setup/workspace.ts — architect role file scaffolding
- lib/setup/smart-model-selector.ts — architect in model assignment
- lib/setup/llm-model-selector.ts — architect in LLM prompt

lib/tools/work-start.ts

@@ -28,14 +28,14 @@ export function createWorkStartTool(api: OpenClawPluginApi) {
       properties: {
         projectGroupId: { type: "string", description: "Project group ID." },
         issueId: { type: "number", description: "Issue ID. If omitted, picks next by priority." },
-        role: { type: "string", enum: ["dev", "qa"], description: "Worker role. Auto-detected from label if omitted." },
+        role: { type: "string", enum: ["dev", "qa", "architect"], description: "Worker role. Auto-detected from label if omitted." },
         level: { type: "string", description: "Developer level (junior/medior/senior/reviewer). Auto-detected if omitted." },
       },
     },
 
     async execute(_id: string, params: Record<string, unknown>) {
       const issueIdParam = params.issueId as number | undefined;
-      const roleParam = params.role as "dev" | "qa" | undefined;
+      const roleParam = params.role as "dev" | "qa" | "architect" | undefined;
       const groupId = params.projectGroupId as string;
       const levelParam = (params.level ?? params.tier) as string | undefined;
       const workspaceDir = requireWorkspaceDir(ctx);