fix(tui): add OSC 8 hyperlinks for wrapped URLs (#17814)

* feat(tui): add OSC 8 hyperlinks to make wrapped URLs clickable

Long URLs that exceed terminal width get broken across lines by pi-tui's
word wrapping, making them unclickable. Post-process rendered markdown
output to add OSC 8 terminal hyperlink sequences around URL fragments,
so each line fragment links to the full URL. Gracefully degrades on
terminals without OSC 8 support.

* tui: harden OSC8 URL extraction and prefix resolution

* tui: add changelog entry for OSC 8 markdown hyperlinks

---------

Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

src/tui/components/assistant-message.ts

@@ -1,12 +1,22 @@
-import { theme } from "../theme/theme.js";
-import { MarkdownMessageComponent } from "./markdown-message.js";
+import { Container, Spacer } from "@mariozechner/pi-tui";
+import { markdownTheme, theme } from "../theme/theme.js";
+import { HyperlinkMarkdown } from "./hyperlink-markdown.js";
+
+export class AssistantMessageComponent extends Container {
+  private body: HyperlinkMarkdown;
 
-export class AssistantMessageComponent extends MarkdownMessageComponent {
   constructor(text: string) {
-    super(text, 0, {
+    super();
+    this.body = new HyperlinkMarkdown(text, 1, 0, markdownTheme, {
       // Keep assistant body text in terminal default foreground so contrast
       // follows the user's terminal theme (dark or light).
       color: (line) => theme.assistantText(line),
     });
+    this.addChild(new Spacer(1));
+    this.addChild(this.body);
+  }
+
+  setText(text: string) {
+    this.body.setText(text);
   }
 }

src/tui/components/hyperlink-markdown.ts

@@ -0,0 +1,37 @@
+import type { Component, DefaultTextStyle, MarkdownTheme } from "@mariozechner/pi-tui";
+import { Markdown } from "@mariozechner/pi-tui";
+import { addOsc8Hyperlinks, extractUrls } from "../osc8-hyperlinks.js";
+
+/**
+ * Wrapper around pi-tui's Markdown component that adds OSC 8 terminal
+ * hyperlinks to rendered output, making URLs clickable even when broken
+ * across multiple lines by word wrapping.
+ */
+export class HyperlinkMarkdown implements Component {
+  private inner: Markdown;
+  private urls: string[];
+
+  constructor(
+    text: string,
+    paddingX: number,
+    paddingY: number,
+    theme: MarkdownTheme,
+    options?: DefaultTextStyle,
+  ) {
+    this.inner = new Markdown(text, paddingX, paddingY, theme, options);
+    this.urls = extractUrls(text);
+  }
+
+  render(width: number): string[] {
+    return addOsc8Hyperlinks(this.inner.render(width), this.urls);
+  }
+
+  setText(text: string): void {
+    this.inner.setText(text);
+    this.urls = extractUrls(text);
+  }
+
+  invalidate(): void {
+    this.inner.invalidate();
+  }
+}