chore: rename marketplace to ythong-harness to avoid name collision

The name 'harness-marketplace' collides with the upstream revfactory/harness
marketplace, so `marketplace add` of this repo was a no-op. Renaming lets this
repo register and coexist as a distinct marketplace.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -1,5 +1,5 @@
 {
-  "name": "harness-marketplace",
+  "name": "ythong-harness",
   "owner": {
     "name": "ythong",
     "email": "ythong86@gmail.com",