Restructure for marketplace: plugin in subdirectory

Move plugin contents into ib-deck-engine/ subdirectory and place
marketplace.json at the root .claude-plugin/ directory. This matches
the structure used by anthropics/financial-services-plugins and is
required for 'claude plugin marketplace add' to work.

Author: gorajin

.claude-plugin/marketplace.json

@@ -3,17 +3,11 @@
   "owner": {
     "name": "gorajing"
   },
-  "metadata": {
-    "description": "Investment banking slide template library for Claude Code. JSON spec → deterministic pixel rendering. Solves cross-model desync, openpyxl corruption, and spatial execution failures.",
-    "version": "0.1.0"
-  },
   "plugins": [
     {
       "name": "ib-deck-engine",
-      "source": ".",
-      "description": "14-template IB slide library. Build pitch decks, football fields, financial summaries, sensitivity grids, sources & uses, trading comps via /ib-deck and friends.",
-      "category": "investment-banking",
-      "tags": ["investment-banking", "powerpoint", "financial-models", "dcf", "lbo", "templates"]
+      "source": "./ib-deck-engine",
+      "description": "14-template investment banking slide library with JSON spec → deterministic pixel rendering. Solves cross-model desync, openpyxl corruption, and spatial execution failures. Includes /ib-deck, /ib-extract, /ib-financial, /ib-football, /ib-comps, /ib-sources-uses, /ib-sensitivity slash commands."
     }
   ]
 }