fix(web): give release notes their own renderer

The update popover rendered release notes with the chat Markdown component.
That component renders raw HTML as live DOM, cannot be mounted in a test (it
resolves katex and mermaid workers, so the popover had to stub it and shipped
unverified), and pulls katex, mermaid and shiki into a 440px panel.

Release notes arrive in one narrow shape we generate ourselves, so render that
shape directly: headings, bullets and paragraphs as real elements through Vue
interpolation, which cannot contribute markup whatever upstream did to the
body. `Built from <url>` leaves the list and becomes a footnote linking the
short commit reference, and only when the URL is an actual web page.

The scroll region is now a tab stop, since notes that outgrow the panel could
not be scrolled without a pointer, and the fade over the last rows appears
only when something is actually below it.

Author: elkaix

.changeset/desktop-release-notes-design.md

@@ -0,0 +1,5 @@
+---
+"@pymodel/pythinker-desktop": patch
+---
+
+Lay out the update release notes as a readable list with the build reference as a footnote, and show when there is more to scroll.

apps/pythinker-code/dist-web/.web-bundle-manifest.json

@@ -1,4 +1,4 @@
 {
-  "sourceHash": "aa9ad464f74ddd042d5435d29ed27bac364c25274ede0eade5d39cc7593d0eb6",
-  "sourceFileCount": 404
+  "sourceHash": "dc4674a73ab1b451eb14a58ba78d954663b5e98dc04ee24b45266716c66a52bb",
+  "sourceFileCount": 405
 }