feat: add per-project default model override for new features (#640)

* feat: add per-project default model override for new features

- Add defaultFeatureModel to ProjectSettings type for project-level override
- Add defaultFeatureModel to Project interface for UI state
- Display Default Feature Model in Model Defaults section alongside phase models
- Include Default Feature Model in global Bulk Replace dialog
- Add Default Feature Model override section to Project Settings
- Add setProjectDefaultFeatureModel store action for project-level overrides
- Update clearAllProjectPhaseModelOverrides to also clear defaultFeatureModel
- Update add-feature-dialog to use project override when available
- Include Default Feature Model in Project Bulk Replace dialog

This allows projects with different complexity levels to use different
default models (e.g., Haiku for simple tasks, Opus for complex projects).

* fix: add server-side __CLEAR__ handler for defaultFeatureModel

- Add handler in settings-service.ts to properly delete defaultFeatureModel
  when '__CLEAR__' marker is sent from the UI
- Fix bulk-replace-dialog.tsx to correctly return claude-opus when resetting
  default feature model to Anthropic Direct (was incorrectly using
  enhancementModel's settings which default to sonnet)

These fixes ensure:
1. Clearing project default model override properly removes the setting
   instead of storing literal '__CLEAR__' string
2. Global bulk replace correctly resets default feature model to opus

* fix: include defaultFeatureModel in Reset to Defaults action

- Updated resetPhaseModels to also reset defaultFeatureModel to claude-opus
- Fixed initial state to use canonical 'claude-opus' instead of 'opus'

* refactor: use DEFAULT_GLOBAL_SETTINGS constant for defaultFeatureModel

Address PR review feedback:
- Replace hardcoded { model: 'claude-opus' } with DEFAULT_GLOBAL_SETTINGS.defaultFeatureModel
- Fix Prettier formatting for long destructuring lines
- Import DEFAULT_GLOBAL_SETTINGS from @automaker/types where needed

This improves maintainability by centralizing the default value.

apps/ui/src/components/views/board-view/dialogs/add-feature-dialog.tsx

@@ -195,8 +195,16 @@ export function AddFeatureDialog({
   const [childDependencies, setChildDependencies] = useState<string[]>([]);
 
   // Get defaults from store
-  const { defaultPlanningMode, defaultRequirePlanApproval, useWorktrees, defaultFeatureModel } =
-    useAppStore();
+  const {
+    defaultPlanningMode,
+    defaultRequirePlanApproval,
+    useWorktrees,
+    defaultFeatureModel,
+    currentProject,
+  } = useAppStore();
+
+  // Use project-level default feature model if set, otherwise fall back to global
+  const effectiveDefaultFeatureModel = currentProject?.defaultFeatureModel ?? defaultFeatureModel;
 
   // Track previous open state to detect when dialog opens
   const wasOpenRef = useRef(false);
@@ -216,7 +224,7 @@ export function AddFeatureDialog({
       );
       setPlanningMode(defaultPlanningMode);
       setRequirePlanApproval(defaultRequirePlanApproval);
-      setModelEntry(defaultFeatureModel);
+      setModelEntry(effectiveDefaultFeatureModel);
 
       // Initialize description history (empty for new feature)
       setDescriptionHistory([]);
@@ -241,7 +249,7 @@ export function AddFeatureDialog({
     defaultBranch,
     defaultPlanningMode,
     defaultRequirePlanApproval,
-    defaultFeatureModel,
+    effectiveDefaultFeatureModel,
     useWorktrees,
     selectedNonMainWorktreeBranch,
     forceCurrentBranchMode,
@@ -343,7 +351,7 @@ export function AddFeatureDialog({
     // When a non-main worktree is selected, use its branch name for custom mode
     setBranchName(selectedNonMainWorktreeBranch || '');
     setPriority(2);
-    setModelEntry(defaultFeatureModel);
+    setModelEntry(effectiveDefaultFeatureModel);
     setWorkMode(
       getDefaultWorkMode(useWorktrees, selectedNonMainWorktreeBranch, forceCurrentBranchMode)
     );