feat(#93): IMP-55 u1~u12 frontend manual section swap detection (manual_section_assignment bool axis + drag-only marker gate + dual-axis persistence + backend manual-true gate)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Front/client/tests/user_overrides_service.test.ts

@@ -559,3 +559,67 @@ describe("saveUserOverrides (IMP-51 #79 u3) — image_overrides axis", () => {
     });
   });
 });
+
+// ============================================================================
+// IMP-55 #93 u1 — manual_section_assignment axis (7th axis) parity coverage
+//
+// The bool intent marker rides on the same per-axis coalescing rails as the
+// 6 sibling axes. These tests lock the typed client behavior so a regression
+// in the boolean serialization (e.g., coercion to "true" string, dropped
+// `false` due to truthy filtering) fails here instead of in Home.tsx (u6/u7)
+// or the backend gate (u9~u11).
+// ============================================================================
+
+describe("saveUserOverrides (IMP-55 #93 u1) — manual_section_assignment axis", () => {
+  it("PUT body carries only manual_section_assignment when it is the sole mutated axis", async () => {
+    fetchMock.mockResolvedValue(mockResponse({}));
+    void saveUserOverrides("03", { manual_section_assignment: true });
+    vi.advanceTimersByTime(300);
+    await drainMicrotasks();
+
+    const body = lastPutBody() as Record<string, unknown>;
+    expect(Object.keys(body)).toEqual(["manual_section_assignment"]);
+    expect(body.manual_section_assignment).toBe(true);
+  });
+
+  it("later-wins coalesces true → false within a single debounce window", async () => {
+    // Drag-then-cancel inside 300 ms — server must see only the final
+    // `false`, not a transient `true` that would re-enable backend
+    // consumption of stale zone_sections.
+    fetchMock.mockResolvedValue(mockResponse({}));
+    void saveUserOverrides("03", { manual_section_assignment: true });
+    void saveUserOverrides("03", { manual_section_assignment: false });
+
+    vi.advanceTimersByTime(300);
+    await drainMicrotasks();
+    expect(putCallsCount()).toBe(1);
+    expect(lastPutBody()).toEqual({ manual_section_assignment: false });
+  });
+
+  it("forwards null sentinel verbatim (explicit clear)", async () => {
+    fetchMock.mockResolvedValue(mockResponse({}));
+    void saveUserOverrides("03", { manual_section_assignment: null });
+
+    vi.advanceTimersByTime(300);
+    await drainMicrotasks();
+    expect(lastPutBody()).toEqual({ manual_section_assignment: null });
+  });
+
+  it("coalesces with zone_sections sibling into a single PUT (drag-drop pair)", async () => {
+    // Real-world drag flow (u6): one save() sets the bool + zone_sections
+    // together. Asserts both axes survive coalescing as a single PUT body.
+    fetchMock.mockResolvedValue(mockResponse({}));
+    void saveUserOverrides("03", {
+      zone_sections: { left: ["03-2"], right: ["03-1"] },
+      manual_section_assignment: true,
+    });
+
+    vi.advanceTimersByTime(300);
+    await drainMicrotasks();
+    expect(putCallsCount()).toBe(1);
+    expect(lastPutBody()).toEqual({
+      zone_sections: { left: ["03-2"], right: ["03-1"] },
+      manual_section_assignment: true,
+    });
+  });
+});