📝 Add Spire to marketplace listings and root README

Spire listed in Claude and Codex marketplace JSONs.
Root README updated: Spire in plugins table + layout tree,
g4b_ai marked deprecated.

.claude-plugin/marketplace.json

@@ -5,10 +5,15 @@
     "email": "gab@g4b.org"
   },
   "plugins": [
+    {
+      "name": "spire",
+      "source": "./plugins/spire",
+      "description": "Agent orchestration system: session coordinator (Igor), domain knowledge agents (adepts), dispatching orchestrator (athanor), knowledge layer (tome), workpad, research tools"
+    },
     {
       "name": "g4b_ai",
       "source": "./plugins/g4b_ai",
-      "description": "Gabor's personal Claude Code skills: workpad, research-tree, implementation-orchestration, markdown-embedded-svg"
+      "description": "Deprecated — use spire. Legacy personal Claude Code skills."
     },
     {
       "name": "dioxus",