perf(ui): lazy-load markdown and defer diff rendering (#215)

## Summary
- lazy-load the markdown and diff render paths so they stop inflating
initial UI startup work
- move shared text rendering helpers out of the markdown path and keep
diff rendering on the deferred path
- defer the Monaco secondary viewers so the markdown and diff path no
longer keeps that work in the main bundle

## Follow-ups
- related fork follow-up: Pagecran/CodeNomad#1
- that follow-up is now independent on dev and only keeps the remaining
right panel, picker, and tool-call secondary chunking work

## Testing
- npm run typecheck --workspace @codenomad/ui
- npm run build --workspace @codenomad/ui

packages/ui/src/components/code-block-inline.tsx

@@ -1,7 +1,8 @@
 import { createSignal, onMount, Show, createEffect } from "solid-js"
 import type { Highlighter } from "shiki/bundle/full"
 import { useTheme } from "../lib/theme"
-import { getSharedHighlighter, escapeHtml } from "../lib/markdown"
+import { getSharedHighlighter } from "../lib/markdown"
+import { escapeHtml } from "../lib/text-render-utils"
 import { copyToClipboard } from "../lib/clipboard"
 import { useI18n } from "../lib/i18n"