feat(windows): добавлен chezmoi-слой для pwsh, terminal и git

- Зачем:
  - нужно перенести стабильную Windows-конфигурацию в dotfiles без поломки существующего stow/install.sh workflow для Linux и WSL.
  - нужно убрать типичные проблемы Git на Windows, включая line endings, из ручной настройки машины.
- Что:
  - добавлен отдельный source dir `chezmoi/` с tiny stub для PowerShell 7 и managed profile в `~/.config/powershell`.
  - добавлены идемпотентная настройка Windows Terminal и managed Git baseline с миграцией локальных настроек в `~/.gitconfig.local`.
  - обновлён README: описан Windows workflow, helper-функции pwsh и состав Git baseline без персональных данных.
- Проверка:
  - `chezmoi -S "$HOME\dotfiles\chezmoi" apply`
  - `pwsh -NoLogo -Command ''$PSVersionTable.PSVersion.ToString(); chcp; [Console]::InputEncoding.WebName; [Console]::OutputEncoding.WebName''`
  - `git config --global --includes --list --show-origin`

chezmoi/.chezmoiscripts/run_before_10-migrate-gitconfig.ps1

@@ -0,0 +1,67 @@
+if (-not $IsWindows) {
+    return
+}
+
+$GlobalGitConfig = Join-Path $HOME '.gitconfig'
+$LocalGitConfig = Join-Path $HOME '.gitconfig.local'
+$BackupPath = '{0}.pre-chezmoi.bak-{1}' -f $GlobalGitConfig, (Get-Date -Format 'yyyyMMdd-HHmmss')
+$ManagedStub = @'
+[include]
+  path = ~/.config/git/config
+
+[include]
+  path = ~/.gitconfig.local
+'@
+
+$ManagedKeys = @(
+    'core.autocrlf',
+    'core.eol',
+    'core.quotepath',
+    'core.longpaths',
+    'fetch.prune',
+    'pull.ff',
+    'init.defaultBranch'
+)
+
+function Test-ManagedGitStub {
+    param(
+        [Parameter(Mandatory = $true)]
+        [string]$Content
+    )
+
+    $NormalizedContent = ($Content -replace "`r", '').Trim()
+    $NormalizedStub = ($ManagedStub -replace "`r", '').Trim()
+    return $NormalizedContent -eq $NormalizedStub
+}
+
+if (-not (Test-Path -LiteralPath $GlobalGitConfig)) {
+    if (-not (Test-Path -LiteralPath $LocalGitConfig)) {
+        New-Item -ItemType File -Path $LocalGitConfig -Force | Out-Null
+    }
+    return
+}
+
+$CurrentContent = Get-Content -LiteralPath $GlobalGitConfig -Raw
+if (Test-ManagedGitStub -Content $CurrentContent) {
+    if (-not (Test-Path -LiteralPath $LocalGitConfig)) {
+        New-Item -ItemType File -Path $LocalGitConfig -Force | Out-Null
+    }
+    return
+}
+
+if (-not (Test-Path -LiteralPath $LocalGitConfig)) {
+    Copy-Item -LiteralPath $GlobalGitConfig -Destination $BackupPath -Force
+    Copy-Item -LiteralPath $GlobalGitConfig -Destination $LocalGitConfig -Force
+
+    foreach ($Key in $ManagedKeys) {
+        git config --file $LocalGitConfig --unset-all $Key 2>$null
+    }
+
+    Write-Host "Migrated existing ~/.gitconfig to ~/.gitconfig.local"
+    Write-Host "Backup saved to: $BackupPath"
+    return
+}
+
+Copy-Item -LiteralPath $GlobalGitConfig -Destination $BackupPath -Force
+Write-Warning "~/.gitconfig.local already exists; current ~/.gitconfig was backed up before managed stub overwrite."
+Write-Host "Backup saved to: $BackupPath"