chore(#653): set npm package author to OpenGSD (#654)

The package author was still the legacy personal credit "TÂCHES", which npm
renders on the package page (issue #653). Set it to the org name OpenGSD,
matching the @opengsd scope / open-gsd org. The installer banner's "by TÂCHES"
was already removed in the #523 rebrand; this clears the last in-repo reference.

Closes #653

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

package.json

@@ -27,7 +27,7 @@
     "codex",
     "codex-cli"
   ],
-  "author": "TÂCHES",
+  "author": "OpenGSD",
   "license": "MIT",
   "repository": {
     "type": "git",