Reduce "Get started" cards on home.mdx to Quickstart and Specification

Pare the `CardGroup` from five cards across three columns down to two
cards across two columns, keeping only Quickstart (pointing at
`/skill-creation/quickstart`) and Specification. The "What are skills?"
card is now redundant with the "What are Agent Skills?", "Why Agent
Skills?", and "How do Agent Skills work?" sections above, and the "Add
skills support", "Example skills", and "Reference library" links serve
smaller audiences that can reach them through the sidebar.

Also rename the section heading to "Get started with Agent Skills" to
match the neighboring sections, and reword the Specification blurb to
reference Agent Skills rather than `SKILL.md` files.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/home.mdx

@@ -54,42 +54,21 @@ The Agent Skills format was originally developed by [Anthropic](https://www.anth
 
 Come join the discussion on [GitHub](https://github.com/agentskills/agentskills) or [Discord](https://discord.gg/MKPE9g8aUy)!
 
-## Get started
+## Get started with Agent Skills
 
-<CardGroup cols={3}>
+<CardGroup cols={2}>
   <Card
-    title="What are skills?"
-    icon="lightbulb"
-    href="/what-are-skills"
+    title="Quickstart"
+    icon="rocket"
+    href="/skill-creation/quickstart"
   >
-    Learn about skills, how they work, and why they matter.
+    Create your first Agent Skill and see it in action.
   </Card>
   <Card
     title="Specification"
     icon="file-code"
     href="/specification"
   >
-    The complete format specification for SKILL.md files.
-  </Card>
-  <Card
-    title="Add skills support"
-    icon="gear"
-    href="/client-implementation/adding-skills-support"
-  >
-    Add skills support to your agent or tool.
-  </Card>
-  <Card
-    title="Example skills"
-    icon="code"
-    href="https://github.com/anthropics/skills"
-  >
-    Browse example skills on GitHub.
-  </Card>
-  <Card
-    title="Reference library"
-    icon="wrench"
-    href="https://github.com/agentskills/agentskills/tree/main/skills-ref"
-  >
-    Validate skills and generate prompt XML.
+    The complete format specification for Agent Skills.
   </Card>
 </CardGroup>