Show the hand cursor when hovering links (RichTextArea renderer)

[koppor]

🤖 PR Description

Problem

Fixes #5.

In the RichTextArea-based renderer (RichHtmlView / RichTextRenderer), hovering a link shows the default text (I-beam) cursor, so a link looks no different from ordinary selectable text. The TextFlow-based FxRenderer already sets Cursor.HAND on its link runs, so the two renderers were inconsistent.

RichTextArea (JavaFX incubator) has no built-in concept of a link cursor — confirmed by the control's author on openjdk/jfx#2196 (comment), who recommended reacting to a custom character StyleAttribute via the control's style-handler registry.

Fix

New rich/HtmlRichTextArea subclass overriding getStyleHandlerRegistry() to return the control's default registry extended with a segment handler for the existing custom HREF attribute. The handler appends -fx-cursor: hand to the run's node through the CellContext — the same mechanism the built-in bold/italic/underline/color handlers use.

• StyleHandlerRegistry.builder(RichTextArea.styleHandlerRegistry) seeds the new registry with all of the control's default handlers, so bold/italic/color/… keep working.
• The skin iterates every attribute on a segment (including custom ones) and calls registry.process(...), so HREF reliably reaches the handler.
• The skin replaces each segment node's whole inline style on every layout, so a recycled node reused for a non-link run does not keep a stale hand cursor — no manual cleanup needed.

Wired into the two construction sites: RichTextRenderer.render(...) and RichHtmlView.

Testing

• ./gradlew build (headless) — green.
• xvfb-run ./gradlew guiTest — green, including the new HtmlRichTextAreaTest, which drives the same StyleHandlerRegistry.process(...) path the skin uses and asserts that a link run requests -fx-cursor:hand, that inherited handlers (bold) still apply, and that a non-link run does not get the hand cursor.

To see it manually: render any HTML containing an <a href> into a RichHtmlView and hover the link — the pointer becomes a hand. (No cursor-on-hover screenshot is attached because screen capture omits the OS cursor.)

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