feat(KB-074): add quick task creation with QuickEntryBox and NewTaskModal

- Add QuickEntryBox component for inline quick task entry in columns
- Add NewTaskModal component with full-featured task creation UI
- Integrate quick create flow through Column → Board → App component hierarchy
- Add comprehensive tests for both new components and updated existing tests
- Add CSS styles for modal, form inputs, and quick entry UI
- Include changeset for @dustinbyrne/kb package release

.changeset/add-quick-entry-and-new-task-modal.md

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+"@dustinbyrne/kb": minor
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+Add Quick Entry Box and New Task Dialog for improved task creation workflow
+
+- **Quick Entry Box**: Minimal input field always visible in Triage column for rapid task creation. Press Enter to immediately create a task.
+- **New Task Modal**: Full-featured dialog opened by the "+ New Task" button with support for:
+  - Title and description
+  - Dependency selection
+  - Model overrides (executor and validator)
+  - Planning mode toggle
+  - Image attachments via drag-drop, paste, or file picker
+- Replaced the previous inline creation card with this two-tier creation experience