Remove completed Issue #50 navigation abort signal task

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Docs/Tasks.md

@@ -1,30 +1,3 @@
-### Issue #50: HIGH - Navigation Abort Signal Timing Bug
-
-**Where found**:
-- `frontend/src/providers/NavigationCancellationProvider.tsx:52-67`
-
-**Why this is needed**:
-The `AbortController` is recreated inside a `useEffect` that fires after render. A request initiated synchronously during the render (before the effect runs) receives the previous cycle's signal — which may already be aborted — and is cancelled immediately instead of completing.
-
-**Goal**:
-Ensure the fresh `AbortController` is available before any request is initiated on a new route.
-
-**What to do**:
-1. Create the new `AbortController` synchronously (outside `useEffect`) when the pathname changes, using `useMemo` or `useRef` with a pathname-keyed guard.
-2. Only abort the old controller inside the effect to avoid aborting the new signal.
-
-**Possible traps and issues**:
-- React strict mode double-invokes effects; ensure the controller is not aborted on the first invocation.
-- `useMemo` is not guaranteed to be stable; prefer `useRef` + pathname comparison.
-
-**Docs changes needed**:
-- Update `frontend/src/providers/PROVIDER_ORDER.md` if the timing contract changes.
-
-**Doc references**:
-- `frontend/src/providers/PROVIDER_ORDER.md`
-
----
-
 ### Issue #51: MEDIUM - Repository Boundary Not Type-Enforced
 
 **Where found**: