refactor(api): extract timeline batch shift support

packages/api/src/__tests__/timeline-allocation-mutation-support.test.ts

@@ -4,8 +4,6 @@ import {
   assertTimelineDateRangeValid,
   buildTimelineAllocationEntryUpdate,
   buildTimelineAllocationMetadata,
-  buildTimelineBatchShiftAuditChanges,
-  shiftTimelineAllocationWindow,
   validateTimelineAllocationDateRanges,
 } from "../router/timeline-allocation-mutation-support.js";
 
@@ -36,59 +34,6 @@ describe("timeline allocation mutation support", () => {
       )).toThrowError(TRPCError);
   });
 
-  it("shifts and clamps allocation windows for each batch-shift mode", () => {
-    expect(
-      shiftTimelineAllocationWindow({
-        startDate: new Date("2026-04-10T00:00:00.000Z"),
-        endDate: new Date("2026-04-12T00:00:00.000Z"),
-        daysDelta: 2,
-        mode: "move",
-      }),
-    ).toEqual({
-      startDate: new Date("2026-04-12T00:00:00.000Z"),
-      endDate: new Date("2026-04-14T00:00:00.000Z"),
-    });
-
-    expect(
-      shiftTimelineAllocationWindow({
-        startDate: new Date("2026-04-10T00:00:00.000Z"),
-        endDate: new Date("2026-04-12T00:00:00.000Z"),
-        daysDelta: 5,
-        mode: "resize-start",
-      }),
-    ).toEqual({
-      startDate: new Date("2026-04-12T00:00:00.000Z"),
-      endDate: new Date("2026-04-12T00:00:00.000Z"),
-    });
-
-    expect(
-      shiftTimelineAllocationWindow({
-        startDate: new Date("2026-04-10T00:00:00.000Z"),
-        endDate: new Date("2026-04-12T00:00:00.000Z"),
-        daysDelta: -5,
-        mode: "resize-end",
-      }),
-    ).toEqual({
-      startDate: new Date("2026-04-10T00:00:00.000Z"),
-      endDate: new Date("2026-04-10T00:00:00.000Z"),
-    });
-  });
-
-  it("builds batch-shift audit payloads", () => {
-    expect(
-      buildTimelineBatchShiftAuditChanges({
-        mode: "move",
-        daysDelta: 3,
-        count: 2,
-      }),
-    ).toEqual({
-      operation: "batchShift",
-      mode: "move",
-      daysDelta: 3,
-      count: 2,
-    });
-  });
-
   it("validates date ranges in bulk", () => {
     expect(() =>
       validateTimelineAllocationDateRanges([