fix: Windows installer missing CLAUDE_CUSTOM_MODELS and other env vars

PS1 installer/updater only set ANTHROPIC_API_KEY and ANTHROPIC_BASE_URL,
missing CLAUDE_CUSTOM_MODELS (required for model picker), AUTH_TOKEN,
default model vars, and telemetry disable vars.

Also added .claude.json pre-configuration (onboarding skip, dark theme)
and mcp__* permission to settings.json.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

codex/codex_config.json

@@ -6,7 +6,6 @@
     "gpt-5.4",
     "gpt-5.3-codex-spark",
     "gpt-5.3-codex",
-    "gpt-5.3",
     "gpt-5.2-codex"
   ],
   "model_reasoning_effort": "xhigh",