fix(core): harden delegation lifecycle, watchdog safety and responsive mobile layout

[Lexus2016]

Summary of Improvements

Addresses edge cases identified during cross-AI peer review (agy & opencode):

• Watchdog safety: Do not evict/recover in_progress tasks that have an active external delegation (activeDelegations).
• Delegation task lifecycle:
  • POST /api/delegate: Reject delegating already completed/cancelled tasks (409) and prevent duplicate concurrent delegations for the same task.
  • DELETE /api/delegate/:id: If delegation was bound to a task that remains in in_progress, revert its status back to todo.
• Kanban dialog viewer & actions:
  • Added real-time polling (2.5s) while #delegationDetailOv is open to display live dialog updates from external agents in sync mode.
  • Check r.ok on delegation messages and stop requests to prevent silent failures.
  • Reset mode radio to handoff upon opening modal for new tasks.
• Responsive UI:
  • Add display: flex !important to .card-actions under @media (max-width: 800px) so action buttons are visible and usable on touch devices without hover.
  • Adjust #cfgModal .modal width to 100% with max-width: calc(100vw - 24px) to avoid horizontal scrollbar overflow.
  • Debounce Kanban tab focus/reconnect resync with a 1500ms latch to eliminate refresh storms.