refactor: Centralize role types and configuration (#190)

Creates a single source of truth for all worker roles via lib/roles/.

## New: lib/roles/

- **registry.ts** — All role definitions (dev, qa, architect) with
  levels, models, emoji, completion results, session key patterns
- **types.ts** — RoleConfig interface
- **selectors.ts** — Query helpers: getRole(), getLevelsForRole(),
  resolveModel(), isValidResult(), roleForLevel(), etc.
- **index.ts** — Barrel exports

## Migrated Files

- **lib/tiers.ts** — Now delegates to registry (backward compat kept)
- **lib/dispatch.ts** — Uses registry for emoji resolution
- **lib/bootstrap-hook.ts** — Uses registry for session key pattern
- **lib/services/tick.ts** — Uses registry for level detection
- **lib/services/heartbeat.ts** — Uses registry for role iteration
- **lib/tools/health.ts** — Uses registry for role iteration
- **lib/tools/work-start.ts** — Uses registry for role enum
- **lib/tools/work-finish.ts** — Uses registry for result validation
- **lib/tools/project-register.ts** — Uses registry for level lists

## Key Benefits

- Adding a new role = add entry to registry.ts (single file)
- No more scattered role unions ("dev" | "qa" | "architect")
- Type-safe role/level/result validation from registry
- Session key pattern auto-generated from registry
- All 64 tests passing (22 new registry tests + 42 existing)

lib/tools/project-register.ts

@@ -14,7 +14,7 @@ import { readProjects, writeProjects, emptyWorkerState } from "../projects.js";
 import { resolveRepoPath } from "../projects.js";
 import { createProvider } from "../providers/index.js";
 import { log as auditLog } from "../audit.js";
-import { DEV_LEVELS, QA_LEVELS, ARCHITECT_LEVELS } from "../tiers.js";
+import { getAllRoleIds, getLevelsForRole } from "../roles/index.js";
 import { DEFAULT_DEV_INSTRUCTIONS, DEFAULT_QA_INSTRUCTIONS, DEFAULT_ARCHITECT_INSTRUCTIONS } from "../templates.js";
 
 /**
@@ -162,9 +162,9 @@ export function createProjectRegisterTool() {
         deployBranch,
         channel,
         roleExecution,
-        dev: emptyWorkerState([...DEV_LEVELS]),
-        qa: emptyWorkerState([...QA_LEVELS]),
-        architect: emptyWorkerState([...ARCHITECT_LEVELS]),
+        dev: emptyWorkerState([...getLevelsForRole("dev")]),
+        qa: emptyWorkerState([...getLevelsForRole("qa")]),
+        architect: emptyWorkerState([...getLevelsForRole("architect")]),
       };
 
       await writeProjects(workspaceDir, data);