Merge branch 'main' (3.16.0) into chore/byterover-tool-mode-sync-3.16

Brings the 3.16.0 release (task cancellation pipeline, settings
infrastructure, update-notifier rework) into the tool-mode branch.

Conflict resolutions:
- src/oclif/commands/{curate,query,dream}: kept ours — tool mode is the
  only dispatch path; main's --cancel <taskId> was for legacy LLM-driven
  long-running tasks that no longer exist on this branch (dream cancel is
  now a subcommand).
- src/tui/components/footer.tsx: kept ours' useAuthStore loading guard +
  main's selectCancelTargetTaskId cancel-task hint. Dropped unused
  useAppViewMode.
- src/tui/providers/app-providers.tsx: kept CancelKeybindInitializer;
  dropped ProviderSubscriptionInitializer (provider feature was removed
  on this branch via ENG-2842).
- src/webui/features/tasks/components/task-list-view.tsx: kept the cancel
  feature wiring; dropped onboarding/tour/composer state (removed on this
  branch via ENG-2842).
- src/webui/features/tasks/components/task-list-table.tsx: renamed
  RowAction → DeleteRowAction to match the auto-merged body refs; dropped
  ProviderChip.
- test/commands/{curate,query}.test.ts: confirmed deletion (legacy
  command-shell tests, replaced by tool-mode test suites).
- package-lock.json: regenerated via npm install.