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/services/heartbeat.ts

@@ -306,7 +306,7 @@ async function performHealthPass(
   const { provider } = await createProvider({ repo: project.repo });
   let fixedCount = 0;
 
-  for (const role of ["dev", "qa"] as const) {
+  for (const role of ["dev", "qa", "architect"] as const) {
     // Check worker health (session liveness, label consistency, etc)
     const healthFixes = await checkWorkerHealth({
       workspaceDir,

lib/services/pipeline.ts

@@ -26,24 +26,28 @@ import {
  * Kept for backward compatibility.
  */
 export const COMPLETION_RULES: Record<string, CompletionRule> = {
-  "dev:done":    { from: "Doing",   to: "To Test",    gitPull: true, detectPr: true },
-  "qa:pass":     { from: "Testing", to: "Done",       closeIssue: true },
-  "qa:fail":     { from: "Testing", to: "To Improve", reopenIssue: true },
-  "qa:refine":   { from: "Testing", to: "Refining" },
-  "dev:blocked": { from: "Doing",   to: "Refining" },
-  "qa:blocked":  { from: "Testing", to: "Refining" },
+  "dev:done":       { from: "Doing",     to: "To Test",    gitPull: true, detectPr: true },
+  "qa:pass":        { from: "Testing",   to: "Done",       closeIssue: true },
+  "qa:fail":        { from: "Testing",   to: "To Improve", reopenIssue: true },
+  "qa:refine":      { from: "Testing",   to: "Refining" },
+  "dev:blocked":    { from: "Doing",     to: "Refining" },
+  "qa:blocked":     { from: "Testing",   to: "Refining" },
+  "architect:done": { from: "Designing", to: "Planning" },
+  "architect:blocked": { from: "Designing", to: "Refining" },
 };
 
 /**
  * @deprecated Use getNextStateDescription() from workflow.ts instead.
  */
 export const NEXT_STATE: Record<string, string> = {
-  "dev:done":    "QA queue",
-  "dev:blocked": "moved to Refining - needs human input",
-  "qa:pass":     "Done!",
-  "qa:fail":     "back to DEV",
-  "qa:refine":   "awaiting human decision",
-  "qa:blocked":  "moved to Refining - needs human input",
+  "dev:done":         "QA queue",
+  "dev:blocked":      "moved to Refining - needs human input",
+  "qa:pass":          "Done!",
+  "qa:fail":          "back to DEV",
+  "qa:refine":        "awaiting human decision",
+  "qa:blocked":       "moved to Refining - needs human input",
+  "architect:done":   "Planning — ready for review",
+  "architect:blocked": "moved to Refining - needs clarification",
 };
 
 // Re-export CompletionRule type for backward compatibility
@@ -77,7 +81,7 @@ export function getRule(
 export async function executeCompletion(opts: {
   workspaceDir: string;
   groupId: string;
-  role: "dev" | "qa";
+  role: "dev" | "qa" | "architect";
   result: string;
   issueId: number;
   summary?: string;

lib/services/tick.ts

@@ -11,7 +11,7 @@ import { createProvider } from "../providers/index.js";
 import { selectLevel } from "../model-selector.js";
 import { getWorker, getSessionForLevel, readProjects } from "../projects.js";
 import { dispatchTask } from "../dispatch.js";
-import { DEV_LEVELS, QA_LEVELS, isDevLevel } from "../tiers.js";
+import { DEV_LEVELS, QA_LEVELS, ARCHITECT_LEVELS, isDevLevel, levelRole } from "../tiers.js";
 import {
   DEFAULT_WORKFLOW,
   getQueueLabels,
@@ -56,10 +56,11 @@ export function detectLevelFromLabels(labels: string[]): string | null {
     const level = l.slice(dot + 1);
     if (role === "dev" && (DEV_LEVELS as readonly string[]).includes(level)) return level;
     if (role === "qa" && (QA_LEVELS as readonly string[]).includes(level)) return level;
+    if (role === "architect" && (ARCHITECT_LEVELS as readonly string[]).includes(level)) return level;
   }
 
   // Fallback: plain level name
-  const all = [...DEV_LEVELS, ...QA_LEVELS] as readonly string[];
+  const all = [...DEV_LEVELS, ...QA_LEVELS, ...ARCHITECT_LEVELS] as readonly string[];
   return all.find((l) => lower.includes(l)) ?? null;
 }
 
@@ -164,7 +165,7 @@ export async function projectTick(opts: {
 
   const provider = opts.provider ?? (await createProvider({ repo: project.repo })).provider;
   const roleExecution = project.roleExecution ?? "parallel";
-  const roles: Role[] = targetRole ? [targetRole] : ["dev", "qa"];
+  const roles: Role[] = targetRole ? [targetRole] : ["dev", "qa", "architect"];
 
   const pickups: TickAction[] = [];
   const skipped: TickResult["skipped"] = [];
@@ -185,7 +186,9 @@ export async function projectTick(opts: {
       skipped.push({ role, reason: `Already active (#${worker.issueId})` });
       continue;
     }
-    if (roleExecution === "sequential" && getWorker(fresh, role === "dev" ? "qa" : "dev").active) {
+    // Check sequential role execution: any other role must be inactive
+    const otherRoles = (["dev", "qa", "architect"] as const).filter(r => r !== role);
+    if (roleExecution === "sequential" && otherRoles.some(r => getWorker(fresh, r).active)) {
       skipped.push({ role, reason: "Sequential: other role active" });
       continue;
     }
@@ -244,10 +247,9 @@ export async function projectTick(opts: {
 function resolveLevelForIssue(issue: Issue, role: Role): string {
   const labelLevel = detectLevelFromLabels(issue.labels);
   if (labelLevel) {
-    // QA role but label specifies a dev level → heuristic picks the right QA level
-    if (role === "qa" && isDevLevel(labelLevel)) return selectLevel(issue.title, issue.description ?? "", role).level;
-    // DEV role but label specifies a QA level → heuristic picks the right dev level
-    if (role === "dev" && !isDevLevel(labelLevel)) return selectLevel(issue.title, issue.description ?? "", role).level;
+    const labelRole = levelRole(labelLevel);
+    // If label level belongs to a different role, use heuristic for correct role
+    if (labelRole && labelRole !== role) return selectLevel(issue.title, issue.description ?? "", role).level;
     return labelLevel;
   }
   return selectLevel(issue.title, issue.description ?? "", role).level;