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/roles/selectors.ts

@@ -0,0 +1,157 @@
+/**
+ * roles/selectors.ts — Query helpers for the role registry.
+ *
+ * All role-related lookups go through these functions.
+ * No other file should access ROLE_REGISTRY directly for role logic.
+ */
+import { ROLE_REGISTRY } from "./registry.js";
+import type { RoleConfig } from "./types.js";
+
+// ---------------------------------------------------------------------------
+// Role IDs
+// ---------------------------------------------------------------------------
+
+/** All registered role IDs. */
+export function getAllRoleIds(): string[] {
+  return Object.keys(ROLE_REGISTRY);
+}
+
+/** The role ID union type, derived from registry. */
+export type WorkerRole = keyof typeof ROLE_REGISTRY;
+
+/** Check if a string is a valid role ID. */
+export function isValidRole(role: string): boolean {
+  return role in ROLE_REGISTRY;
+}
+
+/** Get role config by ID. Returns undefined if not found. */
+export function getRole(role: string): RoleConfig | undefined {
+  return ROLE_REGISTRY[role];
+}
+
+/** Get role config by ID. Throws if not found. */
+export function requireRole(role: string): RoleConfig {
+  const config = ROLE_REGISTRY[role];
+  if (!config) throw new Error(`Unknown role: "${role}". Valid roles: ${getAllRoleIds().join(", ")}`);
+  return config;
+}
+
+// ---------------------------------------------------------------------------
+// Levels
+// ---------------------------------------------------------------------------
+
+/** Get valid levels for a role. */
+export function getLevelsForRole(role: string): readonly string[] {
+  return getRole(role)?.levels ?? [];
+}
+
+/** Get all levels across all roles. */
+export function getAllLevels(): string[] {
+  return Object.values(ROLE_REGISTRY).flatMap(r => [...r.levels]);
+}
+
+/** Check if a level belongs to a specific role. */
+export function isLevelForRole(level: string, role: string): boolean {
+  return getLevelsForRole(role).includes(level);
+}
+
+/** Determine which role a level belongs to. Returns undefined if no match. */
+export function roleForLevel(level: string): string | undefined {
+  for (const [roleId, config] of Object.entries(ROLE_REGISTRY)) {
+    if (config.levels.includes(level)) return roleId;
+  }
+  return undefined;
+}
+
+/** Get the default level for a role. */
+export function getDefaultLevel(role: string): string | undefined {
+  return getRole(role)?.defaultLevel;
+}
+
+// ---------------------------------------------------------------------------
+// Models
+// ---------------------------------------------------------------------------
+
+/** Get default model for a role + level. */
+export function getDefaultModel(role: string, level: string): string | undefined {
+  return getRole(role)?.models[level];
+}
+
+/** Get all default models, nested by role (for config schema). */
+export function getAllDefaultModels(): Record<string, Record<string, string>> {
+  const result: Record<string, Record<string, string>> = {};
+  for (const [roleId, config] of Object.entries(ROLE_REGISTRY)) {
+    result[roleId] = { ...config.models };
+  }
+  return result;
+}
+
+/**
+ * Resolve a level to a full model ID.
+ *
+ * Resolution order:
+ * 1. Plugin config `models.<role>.<level>`
+ * 2. Registry default model
+ * 3. Passthrough (treat level as raw model ID)
+ */
+export function resolveModel(
+  role: string,
+  level: string,
+  pluginConfig?: Record<string, unknown>,
+): string {
+  const models = (pluginConfig as { models?: Record<string, unknown> })?.models;
+  if (models && typeof models === "object") {
+    const roleModels = models[role] as Record<string, string> | undefined;
+    if (roleModels?.[level]) return roleModels[level];
+  }
+  return getDefaultModel(role, level) ?? level;
+}
+
+// ---------------------------------------------------------------------------
+// Emoji
+// ---------------------------------------------------------------------------
+
+/** Get emoji for a role + level. */
+export function getEmoji(role: string, level: string): string | undefined {
+  return getRole(role)?.emoji[level];
+}
+
+/** Get fallback emoji for a role. */
+export function getFallbackEmoji(role: string): string {
+  return getRole(role)?.fallbackEmoji ?? "📋";
+}
+
+// ---------------------------------------------------------------------------
+// Completion
+// ---------------------------------------------------------------------------
+
+/** Get valid completion results for a role. */
+export function getCompletionResults(role: string): readonly string[] {
+  return getRole(role)?.completionResults ?? [];
+}
+
+/** Check if a result is valid for a role. */
+export function isValidResult(role: string, result: string): boolean {
+  return getCompletionResults(role).includes(result);
+}
+
+// ---------------------------------------------------------------------------
+// Session keys
+// ---------------------------------------------------------------------------
+
+/** Build regex pattern that matches any registered role in session keys. */
+export function getSessionKeyRolePattern(): string {
+  return Object.values(ROLE_REGISTRY).map(r => r.sessionKeyPattern).join("|");
+}
+
+// ---------------------------------------------------------------------------
+// Notifications
+// ---------------------------------------------------------------------------
+
+/** Check if a role has a specific notification enabled. */
+export function isNotificationEnabled(
+  role: string,
+  event: "onStart" | "onComplete",
+): boolean {
+  return getRole(role)?.notifications[event] ?? true;
+}