FN-8178: fix task-card context menu autofocus dismissal

Prevent portaled task-card menus from closing when autofocus creates a scroll event.

- Focus the first menu action with preventScroll while preserving keyboard access.
- Cover all card menu entry points and intentional dismissal paths.
- Document the interaction lifecycle fix and publish a patch changeset.

Files changed:
 .changeset/fn-8178-context-menu-flash-dismiss.md   |  7 +++
 docs/dashboard-guide.md                            |  2 +-
 .../task-card-context-menu-flash-dismiss-layers.md | 35 +++++++++++
 .../dashboard/app/components/TaskContextMenu.tsx   |  9 ++-
 .../app/components/__tests__/TaskCard.test.tsx     | 69 ++++++++++++++++++++++
 5 files changed, 120 insertions(+), 2 deletions(-)

Fusion-Task-Id: FN-8178

Fusion-Task-Lineage: 2eb94ffd-e922-497d-8904-1aea8bf760b1

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

docs/solutions/ui-bugs/task-card-context-menu-flash-dismiss-layers.md

@@ -0,0 +1,35 @@
+---
+title: "Task-card popup menus dismiss after autofocus scroll"
+date: 2026-07-16
+category: ui-bugs
+module: packages/dashboard/app/components/TaskContextMenu
+problem_type: interaction_lifecycle_race
+component: dashboard-task-card
+tags:
+  - task-card
+  - context-menu
+  - portal
+  - focus
+  - scroll
+  - fn-8178
+---
+
+# Task-card popup menus dismiss after autofocus scroll
+
+## Problem
+
+A task-card context menu could flash open and immediately dismiss, leaving lifecycle actions unusable. The menu is portaled to `document.body`, but Board card and ListView hosts intentionally listen for capture-phase `scroll` and close an open menu when the operator scrolls.
+
+## Root cause
+
+`TaskContextMenu` automatically focused its first enabled action after mount. In browsers, focusing that fixed, portaled action can scroll a scrollable board ancestor into view. The resulting scroll reached the host's capture-phase dismissal listener, which correctly treated ordinary board scrolling as an explicit dismissal but could not distinguish focus-created scrolling. The result was an open → autofocus → scroll → close loop.
+
+This was not a card stacking-context or outside-pointer containment failure: the popover is a `document.body` portal and its ref correctly recognizes presses inside the menu. All card entry methods converge on the same mounted `TaskContextMenu`, so ⋯ click, right-click, touch/pen long-press, and keyboard context-menu access shared the fault.
+
+## Resolution
+
+Keep automatic keyboard focus, but call `focus({ preventScroll: true })` for the first enabled menu item. This prevents the synthetic scroll while preserving intentional dismissal on item selection, outside pointerdown, Escape, and real board scrolling. Because `TaskContextMenu` is shared, ListView and Task Detail also retain their focus behavior without duplicated lifecycle guards.
+
+## Regression coverage
+
+The TaskCard suite simulates a browser that dispatches a scroll after default focus and verifies that each card entry method remains open with `preventScroll`, invokes its action, and still honors outside-click, Escape, and real-scroll dismissal.