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

packages/dashboard/app/components/QuickEntryBox.tsx

@@ -0,0 +1,64 @@
+import { useState, useCallback, useRef } from "react";
+import type { ToastType } from "../hooks/useToast";
+
+interface QuickEntryBoxProps {
+  onCreate: (description: string) => Promise<void>;
+  addToast: (message: string, type?: ToastType) => void;
+}
+
+export function QuickEntryBox({ onCreate, addToast }: QuickEntryBoxProps) {
+  const [description, setDescription] = useState("");
+  const [isSubmitting, setIsSubmitting] = useState(false);
+  const inputRef = useRef<HTMLInputElement>(null);
+
+  const handleSubmit = useCallback(async () => {
+    const trimmed = description.trim();
+    if (!trimmed || isSubmitting) return;
+
+    setIsSubmitting(true);
+    try {
+      await onCreate(trimmed);
+      // Clear input and keep focus for rapid entry
+      setDescription("");
+      // Focus stays on input for next entry
+      inputRef.current?.focus();
+    } catch (err: any) {
+      addToast(err.message || "Failed to create task", "error");
+      // Keep input content on failure so user can retry
+    } finally {
+      setIsSubmitting(false);
+    }
+  }, [description, isSubmitting, onCreate, addToast]);
+
+  const handleKeyDown = useCallback(
+    (e: React.KeyboardEvent<HTMLInputElement>) => {
+      if (e.key === "Enter") {
+        e.preventDefault();
+        handleSubmit();
+      } else if (e.key === "Escape") {
+        e.preventDefault();
+        if (description.trim()) {
+          // Clear non-empty input on Escape
+          setDescription("");
+        }
+      }
+    },
+    [handleSubmit, description],
+  );
+
+  return (
+    <div className="quick-entry-box" data-testid="quick-entry-box">
+      <input
+        ref={inputRef}
+        type="text"
+        className="quick-entry-input"
+        placeholder={isSubmitting ? "Creating..." : "Add a task..."}
+        value={description}
+        onChange={(e) => setDescription(e.target.value)}
+        onKeyDown={handleKeyDown}
+        disabled={isSubmitting}
+        data-testid="quick-entry-input"
+      />
+    </div>
+  );
+}