fix: TOML dotted key bug + PowerShell fallback for all Windows scripts

- codex: add [notice.model_migrations] with quoted keys to prevent
  Codex from writing unquoted dotted keys (gpt-5.4 → gpt-5 → 4)
  which causes "invalid type: map, expected a string" TOML error
- codex_patcher.py: add toml_key() to quote keys with dots,
  handle broken TOML gracefully in read_toml()
- claude install: remove unnecessary Python requirement
- claude update: rewrite as standalone (no git clone dependency)
- gemini update: add Python check with fallback, auth headers
- qwen install: add PowerShell fallback, auth headers, no exit on no Python
- qwen update: add Python check with fallback, auth headers

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

claude/uclaude_install.ps1

@@ -32,19 +32,6 @@ function Get-NodeMajor {
 
 # ---- Check prerequisites ----
 
-# Python
-if (-not (Test-Command "python3") -and -not (Test-Command "python")) {
-    Write-Host "  Python not found. Installing..." -ForegroundColor Yellow
-    if (Test-Command "winget") {
-        winget install --id Python.Python.3.12 --accept-package-agreements --accept-source-agreements -e 2>$null
-        Refresh-Path
-    } else {
-        Write-Host "  Install Python manually: https://www.python.org/downloads/" -ForegroundColor Red
-        exit 1
-    }
-}
-Write-Host "  Python OK" -ForegroundColor Green
-
 # Node.js >= 20
 $MIN_NODE_MAJOR = 20
 $nodeMajor = Get-NodeMajor