feat(FN-4068): add branch conflict detection and recovery for stale worktre

Implements branch conflict detection and recovery across the Fusion engine, CLI, and dashboard — surfacing git worktree conflicts when tasks conflict with unrelated branch state, and providing a recovery workflow to resolve them. The executor and worktree pool now integrate typed branch conflict che

Fusion-Task-Id: FN-4068

packages/core/src/__tests__/settings-parity.test.ts

@@ -73,6 +73,12 @@ describe("settings key parity", () => {
     expect(DEFAULT_PROJECT_SETTINGS.heartbeatMultiplier).toBe(1);
   });
 
+  it("defaults sibling branch rename escape hatch to disabled", () => {
+    expect(DEFAULT_PROJECT_SETTINGS.executorAllowSiblingBranchRename).toBe(false);
+    expect(isProjectSettingsKey("executorAllowSiblingBranchRename")).toBe(true);
+    expect(isGlobalSettingsKey("executorAllowSiblingBranchRename")).toBe(false);
+  });
+
   it("defaults completionDocumentationMode to off", () => {
     expect(DEFAULT_PROJECT_SETTINGS.completionDocumentationMode).toBe("off");
   });