Add reusable bounded integer inputs for JavaFX editors

fx/docs/integer-spinners.md

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+# Bounded integer inputs
+
+`de.neitzel.fx.control.IntegerSpinners.nonNegative(min, max, value)` creates an
+editable JavaFX spinner with inclusive nonnegative bounds. Construct and use it
+on the JavaFX application thread.
+
+Every valid typed number immediately updates the value property, so a form can
+save its model without waiting for Enter or a focus change. Non-digit input and
+values above the maximum are rejected. Empty input and intermediate numbers
+below the minimum retain the last committed value and revert when focus leaves
+the editor. Increment/decrement use the normal JavaFX spinner behavior.
+
+The factory rejects negative/inverted bounds and out-of-range initial values.
+Applications own their field labels, units, and domain-specific bounds.

fx/src/main/java/de/neitzel/fx/control/IntegerSpinners.java

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+package de.neitzel.fx.control;
+
+import javafx.scene.control.Spinner;
+import javafx.scene.control.TextFormatter;
+
+/** Factories for bounded integer inputs that commit valid typing immediately. */
+public final class IntegerSpinners {
+    private IntegerSpinners() {
+    }
+
+    /**
+     * Creates a nonnegative bounded input. Valid typing immediately updates its value;
+     * incomplete values below the minimum revert to the committed value on focus loss.
+     *
+     * @param min inclusive nonnegative minimum
+     * @param max inclusive maximum
+     * @param value initial value
+     * @return an editable spinner
+     */
+    public static Spinner<Integer> nonNegative(int min, int max, int value) {
+        if (min < 0 || max < min || value < min || value > max) {
+            throw new IllegalArgumentException("Invalid nonnegative spinner bounds or value");
+        }
+        Spinner<Integer> spinner = new Spinner<>(min, max, value);
+        spinner.setEditable(true);
+        spinner.getEditor().setTextFormatter(new TextFormatter<String>(change -> {
+            String text = change.getControlNewText();
+            if (!text.matches("\\d{0,10}")) {
+                return null;
+            }
+            if (!text.isEmpty() && Long.parseLong(text) > max) {
+                return null;
+            }
+            return change;
+        }));
+        spinner.getEditor().textProperty().addListener((observable, old, text) -> {
+            if (!text.isEmpty()) {
+                int parsed = Integer.parseInt(text);
+                if (parsed >= min) {
+                    spinner.getValueFactory().setValue(parsed);
+                }
+            }
+        });
+        spinner.getEditor().focusedProperty().addListener((observable, old, focused) -> {
+            if (!focused) {
+                spinner.getEditor().setText(spinner.getValue().toString());
+            }
+        });
+        return spinner;
+    }
+}