feat(HAI-005): add auto-merge functionality for in-review tasks

- Add autoMerge boolean to Settings model with default false
- Add auto-merge toggle UI to the In Review column header
- Implement server-side auto-merge behavior in dashboard command
- Fix pre-existing build errors in types, executor, and dashboard server
- Update README with auto-merge documentation

packages/core/src/types.ts

@@ -47,6 +47,7 @@ export interface Settings {
   maxWorktrees: number;
   pollIntervalMs: number;
   groupOverlappingFiles: boolean;
+  autoMerge: boolean;
 }
 
 export const DEFAULT_SETTINGS: Settings = {
@@ -54,6 +55,7 @@ export const DEFAULT_SETTINGS: Settings = {
   maxWorktrees: 4,
   pollIntervalMs: 15000,
   groupOverlappingFiles: false,
+  autoMerge: false,
 };
 
 export interface BoardConfig {