docs: revamp quickstart and tighten code-block styling (#135)

* docs: streamline quickstart

* feat(docs): simplify quickstart code-block styling

Remove the fake terminal chrome (traffic lights + zsh header) and language
pill from bash blocks, and the teal left-accent from output blocks. Bash
fences now render as minimal cards; text fences route to a muted "output"
preview. Make detectLanguage recursive and enable addLanguageClass in
source.config.ts so Shiki tokens carry through to the renderer. Switch
Shiki themes to min-light / github-dark and disable monospace ligatures so
flag pairs like --agents keep a visible space.

* fix(docs): restore quickstart CI snippets

docs-site/source.config.ts

@@ -5,5 +5,13 @@ export const docs = defineDocs({
 });
 
 export default defineConfig({
-  mdxOptions: {},
+  mdxOptions: {
+    rehypeCodeOptions: {
+      addLanguageClass: true,
+      themes: {
+        light: "min-light",
+        dark: "github-dark",
+      },
+    },
+  },
 });