feat(KB-184): change autoMerge default from false to true

- Update DEFAULT_SETTINGS in core types to set autoMerge: true
- Update initial state defaults in App and SettingsModal components
- Update test fixtures in App, Board, and SettingsModal tests
- Update kb-board skill docs to reflect new default
- Add minor changeset for the default change

packages/dashboard/app/components/__tests__/App.test.tsx

@@ -8,7 +8,7 @@ const defaultSettings: Settings = {
   maxWorktrees: 4,
   pollIntervalMs: 15000,
   groupOverlappingFiles: false,
-  autoMerge: false,
+  autoMerge: true,
   recycleWorktrees: false,
   worktreeInitCommand: "",
   testCommand: "",

packages/dashboard/app/components/__tests__/Board.test.tsx

@@ -25,7 +25,7 @@ function renderBoard() {
       onCancelCreate={noop}
       onCreateTask={noopAsync}
       onNewTask={noop}
-      autoMerge={false}
+      autoMerge={true}
       onToggleAutoMerge={noop}
       globalPaused={false}
     />,

packages/dashboard/app/components/__tests__/SettingsModal.test.tsx

@@ -8,7 +8,7 @@ const defaultSettings: Settings = {
   maxWorktrees: 4,
   pollIntervalMs: 15000,
   groupOverlappingFiles: false,
-  autoMerge: false,
+  autoMerge: true,
   recycleWorktrees: false,
   worktreeInitCommand: "",
   testCommand: "",