fix(timeline): stabilize popovers on internal scroll + expand test coverage

B-1: useViewportPopover — ignoreScrollContainers option; scroll events
originating inside the timeline canvas no longer close point-anchor popovers
B-2: AllocationPopover, DemandPopover, NewAllocationPopover — thread
scrollContainerRef through so horizontal timeline scroll is ignored
B-3: AllocationPopover — staleTime 0 so SSE reconnect triggers immediate refetch
B-4: useViewportPopover.test.ts — 6 new tests (scroll close, ignore container,
resize close, style clamping)
B-5: AllocationPopover.test.tsx — loading state + happy-path tests added

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/components/timeline/DemandPopover.tsx

@@ -1,5 +1,6 @@
 "use client";
 
+import type { RefObject } from "react";
 import { createPortal } from "react-dom";
 import type { TimelineDemandEntry } from "./TimelineContext.js";
 import { formatCents, formatDateLong } from "~/lib/format.js";
@@ -12,6 +13,7 @@ interface DemandPopoverProps {
   onFillDemand: (demand: TimelineDemandEntry) => void;
   anchorX: number;
   anchorY: number;
+  ignoreScrollContainers?: RefObject<HTMLElement | null>[];
 }
 
 export function DemandPopover({
@@ -21,12 +23,14 @@ export function DemandPopover({
   onFillDemand,
   anchorX,
   anchorY,
+  ignoreScrollContainers,
 }: DemandPopoverProps) {
   const { ref, style } = useViewportPopover({
     anchor: { kind: "point", x: anchorX, y: anchorY },
     width: 300,
     estimatedHeight: 340,
     onClose,
+    ...(ignoreScrollContainers ? { ignoreScrollContainers } : {}),
   });
 
   const roleName = demand.roleEntity?.name ?? demand.role ?? "Unspecified";