Name the marketplace after us, not after one platform

Apple work is what exists today, but the methodology skills sitting
unversioned in ~/.claude/skills are the same problem and will want the
same home. A marketplace name is the key users register it under, so
renaming later would mean everyone removing and re-adding it. Cheaper to
be right now.

Marketplace is `pdat`, repository is claude-plugins, and the install
lines carry the real Gitea URL.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -1,11 +1,11 @@
 {
-  "name": "pdat-xcode",
+  "name": "pdat",
   "owner": {
     "name": "PDAT s.r.o.",
     "email": "tomas.uvira@pdat.cz"
   },
   "metadata": {
-    "description": "Practices for building Apple platform apps with Claude Code, learned from shipping them."
+    "description": "PDAT's Claude Code plugins: practices and findings for the platforms we build on."
   },
   "plugins": [
     {