feat: add Windows PowerShell support and remote install one-liners

- remote-install.sh: POSIX one-liner (curl | sh), downloads archive to tmpdir
- remote-install.ps1: Windows one-liner (irm | iex), fully native PowerShell
- install.ps1: Native Windows installer calling all .ps1 post-install scripts
- bin/mosaic-link-runtime-assets.ps1: Syncs runtime config files
- bin/mosaic-sync-skills.ps1: Clones skills, links via directory junctions
- bin/mosaic-migrate-local-skills.ps1: Migrates local skills to junctions
- bin/mosaic-doctor.ps1: Health audit for Windows environments

Directory junctions used instead of symlinks (no elevation required).
All junction operations fall back to file copy on failure.

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

install.ps1

@@ -0,0 +1,70 @@
+# Mosaic Bootstrap — Windows Installer
+# PowerShell equivalent of install.sh
+#
+# Usage:
+#   powershell -ExecutionPolicy Bypass -File install.ps1
+#
+$ErrorActionPreference = "Stop"
+
+$SourceDir = $PSScriptRoot
+$TargetDir = if ($env:MOSAIC_HOME) { $env:MOSAIC_HOME } else { Join-Path $env:USERPROFILE ".config\mosaic" }
+
+if (-not (Test-Path $TargetDir)) { New-Item -ItemType Directory -Path $TargetDir -Force | Out-Null }
+
+# Sync files: remove old content, copy new
+Write-Host "[mosaic-install] Copying framework to $TargetDir..."
+Get-ChildItem $TargetDir -Exclude ".git" | Remove-Item -Recurse -Force
+Get-ChildItem $SourceDir -Exclude ".git" | ForEach-Object {
+    $dest = Join-Path $TargetDir $_.Name
+    if ($_.PSIsContainer) {
+        Copy-Item $_.FullName $dest -Recurse -Force
+    }
+    else {
+        Copy-Item $_.FullName $dest -Force
+    }
+}
+
+Write-Host "[mosaic-install] Installed framework to $TargetDir"
+
+# Run post-install scripts (PowerShell versions)
+$binDir = Join-Path $TargetDir "bin"
+
+Write-Host "[mosaic-install] Linking runtime compatibility assets"
+try {
+    & "$binDir\mosaic-link-runtime-assets.ps1"
+}
+catch {
+    Write-Host "[mosaic-install] WARNING: runtime asset linking failed (framework install still complete)" -ForegroundColor Yellow
+}
+
+Write-Host "[mosaic-install] Syncing universal skills"
+if ($env:MOSAIC_SKIP_SKILLS_SYNC -eq "1") {
+    Write-Host "[mosaic-install] Skipping skills sync (MOSAIC_SKIP_SKILLS_SYNC=1)"
+}
+else {
+    try {
+        & "$binDir\mosaic-sync-skills.ps1"
+    }
+    catch {
+        Write-Host "[mosaic-install] WARNING: skills sync failed (framework install still complete)" -ForegroundColor Yellow
+    }
+}
+
+Write-Host "[mosaic-install] Migrating runtime-local skills to Mosaic junctions"
+try {
+    & "$binDir\mosaic-migrate-local-skills.ps1" -Apply
+}
+catch {
+    Write-Host "[mosaic-install] WARNING: local skill migration failed (framework install still complete)" -ForegroundColor Yellow
+}
+
+Write-Host "[mosaic-install] Running health audit"
+try {
+    & "$binDir\mosaic-doctor.ps1"
+}
+catch {
+    Write-Host "[mosaic-install] WARNING: doctor reported issues (run mosaic-doctor.ps1 -FailOnWarn)" -ForegroundColor Yellow
+}
+
+Write-Host "[mosaic-install] Done."
+Write-Host "[mosaic-install] Add to PATH: `$env:USERPROFILE\.config\mosaic\bin"