feat(HAI-004): add settings modal with GET/PUT API endpoints

- Extend config schema and store helpers to support settings persistence
- Add GET/PUT /settings REST API endpoints in dashboard routes
- Create SettingsModal component with frontend API wiring
- Add settings trigger button to Header and integrate into App
- Add CSS styles for settings modal and header actions

packages/core/src/index.ts

@@ -1,4 +1,4 @@
-export { COLUMNS, COLUMN_LABELS, COLUMN_DESCRIPTIONS, VALID_TRANSITIONS } from "./types.js";
-export type { Column, Task, TaskCreateInput, TaskDetail, BoardConfig, MergeResult } from "./types.js";
+export { COLUMNS, COLUMN_LABELS, COLUMN_DESCRIPTIONS, VALID_TRANSITIONS, DEFAULT_SETTINGS } from "./types.js";
+export type { Column, Task, TaskCreateInput, TaskDetail, BoardConfig, MergeResult, Settings } from "./types.js";
 export { TaskStore } from "./store.js";
 export { canTransition, getValidTransitions, resolveDependencyOrder } from "./board.js";

packages/core/src/store.ts

@@ -3,8 +3,8 @@ import { execSync } from "node:child_process";
 import { mkdir, readFile, writeFile, readdir } from "node:fs/promises";
 import { join, sep } from "node:path";
 import { existsSync, watch, type FSWatcher } from "node:fs";
-import type { Task, TaskDetail, TaskCreateInput, BoardConfig, Column, MergeResult } from "./types.js";
-import { VALID_TRANSITIONS } from "./types.js";
+import type { Task, TaskDetail, TaskCreateInput, BoardConfig, Column, MergeResult, Settings } from "./types.js";
+import { VALID_TRANSITIONS, DEFAULT_SETTINGS } from "./types.js";
 
 export interface TaskStoreEvents {
   "task:created": [task: Task];
@@ -44,6 +44,20 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     }
   }
 
+  async getSettings(): Promise<Settings> {
+    const config = await this.readConfig();
+    return { ...DEFAULT_SETTINGS, ...config.settings };
+  }
+
+  async updateSettings(patch: Partial<Settings>): Promise<Settings> {
+    const config = await this.readConfig();
+    const current = { ...DEFAULT_SETTINGS, ...config.settings };
+    const updated = { ...current, ...patch };
+    config.settings = updated;
+    await this.writeConfig(config);
+    return updated;
+  }
+
   private async readConfig(): Promise<BoardConfig> {
     const data = await readFile(this.configPath, "utf-8");
     return JSON.parse(data);

packages/core/src/types.ts

@@ -24,8 +24,19 @@ export interface TaskCreateInput {
   dependencies?: string[];
 }
 
+export interface Settings {
+  maxConcurrent: number;
+  pollIntervalMs: number;
+}
+
+export const DEFAULT_SETTINGS: Settings = {
+  maxConcurrent: 2,
+  pollIntervalMs: 15000,
+};
+
 export interface BoardConfig {
   nextId: number;
+  settings?: Settings;
 }
 
 export interface MergeResult {