feat(hook-message-injector): enhance boulder continuation injector with lineage support

- Add lineage-aware continuation injection logic
- Support for tracking multiple session types (direct vs appended)
- Update tests for new lineage continuation scenarios
- Add session origin validation in continuation flow

🤖 Generated with assistance of OhMyOpenCode

src/hooks/atlas/boulder-continuation-injector.test.ts

@@ -41,14 +41,8 @@ describe("injectBoulderContinuation", () => {
       sessionState: { promptFailureCount: 0 },
     })
 
-<<<<<<< HEAD
-    // then
-    expect(result).toBe("injected")
-||||||| parent of 1b39490a (fix(atlas): use raw agent key instead of display name for API calls (#3138))
-    // then
-=======
     // then - uses raw agent key, not display name (to avoid HTTP header validation issues)
->>>>>>> 1b39490a (fix(atlas): use raw agent key instead of display name for API calls (#3138))
+    expect(result).toBe("injected")
     expect(promptAsyncMock).toHaveBeenCalledTimes(1)
     expect(promptAsyncMock).toHaveBeenCalledWith(
       expect.objectContaining({