chore(vscode): prepare for Marketplace publishing

- Fix publisher to lowercase 'ryanbasmajian' to match Marketplace ID
- Convert marketplace icon from 16-bit to 8-bit PNG (fixes upload error)
- Lower engines.vscode to ^1.85.0 for broader compatibility

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ryanbas21

packages/vscode-extension/icons/oidc-devtools-marketplace.png

@@ -3,7 +3,7 @@
   "displayName": "OIDC DevTools",
   "description": "Live OIDC/OAuth2 debugging — network capture, SDK event correlation, and flow diagnosis via Chrome DevTools Protocol",
   "version": "0.1.0",
-  "publisher": "RyanBasmajian",
+  "publisher": "ryanbasmajian",
   "license": "MIT",
   "repository": {
     "type": "git",
@@ -13,7 +13,7 @@
   "icon": "icons/oidc-devtools-marketplace.png",
   "keywords": ["oidc", "oauth", "oauth2", "authentication", "debugger", "devtools", "chrome", "cdp"],
   "engines": {
-    "vscode": "^1.100.0"
+    "vscode": "^1.85.0"
   },
   "categories": ["Debuggers", "Other"],
   "activationEvents": [
@@ -127,7 +127,7 @@
     "ws": "^8.18.0"
   },
   "devDependencies": {
-    "@types/vscode": "^1.100.0",
+    "@types/vscode": "^1.85.0",
     "@types/ws": "^8.18.0",
     "@vscode/vsce": "^3.0.0",
     "esbuild": "^0.28.0"