feat(whats-new): render standalone release-note links as clickable

The What's New / release-notes modal renders the GitHub release body through a
custom block model that stripped inline markup and had no link support, so a
markdown link showed as literal `[text](url)`. Now:
- inline links `[text](url)` collapse to just their text (clean attributions),
- a whole-line link becomes a KIND_LINK block rendered as a clickable accent
  link opened in the browser (a new WhatsNewActions.open-url reusing open::that,
  mirroring about.rs).

Adds a `url` field to WhatsNewBlock plus a small markdown-link parser. The 2.0.2
notes use it for the daemon-wiki link. Built + smoked at release (window ready,
ALSA 192kHz bit-perfect, playback OK).

cc

crates/qbz-ui/ui/shell/WhatsNewModal.slint

@@ -177,7 +177,8 @@ export component WhatsNewModal inherits Rectangle {
                                     font-size: block.level >= 2 ? 11px : 12px;
                                 }
 
-                                Text {
+                                // Section / bullet / paragraph text (kinds 0-2).
+                                if block.kind != 3: Text {
                                     text: block.text;
                                     horizontal-stretch: 1;
                                     wrap: word-wrap;
@@ -195,6 +196,26 @@ export component WhatsNewModal inherits Rectangle {
                                         ? Typography.bold
                                         : Typography.regular;
                                 }
+
+                                // Whole-line link (kind 3) — a clickable accent link.
+                                if block.kind == 3: Rectangle {
+                                    horizontal-stretch: 1;
+                                    height: link-text.preferred-height;
+                                    link-text := Text {
+                                        text: block.text;
+                                        width: 100%;
+                                        wrap: word-wrap;
+                                        color: link-ta.has-hover ? Theme.accent-hover : Theme.accent;
+                                        font-size: 13px;
+                                        font-weight: Typography.medium;
+                                    }
+                                    link-ta := TouchArea {
+                                        mouse-cursor: pointer;
+                                        clicked => {
+                                            WhatsNewActions.open-url(block.url);
+                                        }
+                                    }
+                                }
                             }
 
                             Rectangle { height: 8px; }

crates/qbz-ui/ui/state.slint

@@ -5915,6 +5915,7 @@ export struct WhatsNewBlock {
     level: int,
     text: string,
     id: string,
+    url: string,
 }
 
 // One table-of-contents entry (level-0 section headings only).
@@ -5937,4 +5938,6 @@ export global WhatsNewActions {
     // Open the modal AND kick off the GitHub release fetch (Rust).
     callback open();
     callback close();
+    // Open an external URL from a standalone release-notes link (Rust: open::that).
+    callback open-url(string);
 }