fix(install): address Codex review — guard reparse deletes and robust uninstall

- install.ps1 (P1): refuse to delete real files/directories; only remove
  paths that are actual junctions/symlinks. Closes a data-loss path where
  Cmd-Uninstall would Remove-Item -Recurse a pre-existing user directory at
  ~/.understand-anything-plugin (Cmd-Install correctly skipped touching it,
  but uninstall did not). Cmd-Uninstall and Unlink-Skills now both go
  through Remove-Reparse, which uses DirectoryInfo.Delete() so a junction's
  target is never followed.

- install.sh (P2): --uninstall no longer exits early when the checkout has
  been deleted. The per-skill unlinker falls back to scanning the target
  dir for stale symlinks pointing into the plugin tree, so users can clean
  up after manually rm -rf'ing the checkout.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

install.ps1

@@ -97,8 +97,34 @@ function Get-SkillNames {
     Get-ChildItem -Path $root -Directory | Select-Object -ExpandProperty Name
 }
 
+function Test-IsReparse([string]$Path) {
+    if (-not (Test-Path $Path)) { return $false }
+    $item = Get-Item -LiteralPath $Path -Force
+    return ($item.LinkType -eq 'Junction' -or $item.LinkType -eq 'SymbolicLink')
+}
+
+function Remove-Reparse([string]$Path) {
+    # Removes a junction/symlink without touching its target. Refuses to touch
+    # real files or directories so an existing user folder at the same path is
+    # never destroyed.
+    if (-not (Test-Path $Path)) { return $false }
+    $item = Get-Item -LiteralPath $Path -Force
+    if ($item.LinkType -eq 'Junction' -or $item.LinkType -eq 'SymbolicLink') {
+        $item.Delete()
+        return $true
+    }
+    Write-Warning "Refusing to delete $Path — it is a real file/directory, not a junction/symlink we created. Remove it manually if you intended to."
+    return $false
+}
+
 function New-Junction([string]$LinkPath, [string]$TargetPath) {
-    if (Test-Path $LinkPath) { Remove-Item -Force -Recurse $LinkPath }
+    if (Test-Path $LinkPath) {
+        if (Test-IsReparse $LinkPath) {
+            (Get-Item -LiteralPath $LinkPath -Force).Delete()
+        } else {
+            Write-Error "Refusing to overwrite $LinkPath — it is a real file/directory, not a junction. Move or remove it first."
+        }
+    }
     New-Item -ItemType Junction -Path $LinkPath -Target $TargetPath | Out-Null
 }
 
@@ -125,16 +151,28 @@ function Link-Skills([string]$Target, [string]$Style) {
 }
 
 function Unlink-Skills([string]$Target, [string]$Style) {
+    if (-not (Test-Path $Target)) { return }
     switch ($Style) {
         'per-skill' {
-            foreach ($skill in Get-SkillNames) {
-                $link = Join-Path $Target $skill
-                if (Test-Path $link) { Remove-Item -Force -Recurse $link }
+            $skillsRoot = Get-SkillsRoot
+            if (Test-Path $skillsRoot) {
+                foreach ($skill in Get-SkillNames) {
+                    Remove-Reparse (Join-Path $Target $skill) | Out-Null
+                }
+            } else {
+                # Checkout is gone — scan the target dir for stale links pointing
+                # into our plugin tree so we can still clean up.
+                Get-ChildItem -LiteralPath $Target -Force | ForEach-Object {
+                    if ($_.LinkType -eq 'Junction' -or $_.LinkType -eq 'SymbolicLink') {
+                        if ($_.Target -match 'understand-anything-plugin[\\/]+skills[\\/]+') {
+                            Remove-Reparse $_.FullName | Out-Null
+                        }
+                    }
+                }
             }
         }
         'folder' {
-            $link = Join-Path $Target 'understand-anything'
-            if (Test-Path $link) { Remove-Item -Force -Recurse $link }
+            Remove-Reparse (Join-Path $Target 'understand-anything') | Out-Null
         }
     }
 }
@@ -167,18 +205,15 @@ function Cmd-Install([string]$Id) {
 
 function Cmd-Uninstall([string]$Id) {
     $cfg = Resolve-Platform $Id
-    if (-not (Test-Path $RepoDir)) {
-        Write-Host "No checkout found at $RepoDir — nothing to unlink."
-        return
-    }
     Write-Host "→ Removing skill links for $Id"
     Unlink-Skills $cfg.Target $cfg.Style
-    if (Test-Path $PluginLink) {
-        Remove-Item -Force -Recurse $PluginLink
+    if (Remove-Reparse $PluginLink) {
         Write-Host "  ✓ removed $PluginLink"
     }
-    Write-Host "`nThe checkout at $RepoDir was kept (other platforms may still use it)."
-    Write-Host "To remove it: Remove-Item -Recurse -Force '$RepoDir'"
+    if (Test-Path $RepoDir) {
+        Write-Host "`nThe checkout at $RepoDir was kept (other platforms may still use it)."
+        Write-Host "To remove it: Remove-Item -Recurse -Force '$RepoDir'"
+    }
 }
 
 function Cmd-Update {

install.sh

@@ -136,15 +136,28 @@ link_skills() {
 
 unlink_skills() {
   local target="$1" style="$2"
+  [[ -d "$target" ]] || return 0
   case "$style" in
     per-skill)
-      local skill
-      while IFS= read -r skill; do
-        rm -f "$target/$skill"
-      done < <(list_skills)
+      if [[ -d "$(skills_root)" ]]; then
+        local skill
+        while IFS= read -r skill; do
+          [[ -L "$target/$skill" ]] && rm -f "$target/$skill"
+        done < <(list_skills)
+      else
+        # Checkout is gone — scan the target dir for stale links pointing into
+        # our plugin tree so we can still clean up.
+        local link resolved
+        for link in "$target"/*; do
+          [[ -L "$link" ]] || continue
+          resolved="$(readlink "$link" 2>/dev/null || true)"
+          [[ "$resolved" == *"/understand-anything-plugin/skills/"* ]] || continue
+          rm -f "$link"
+        done
+      fi
       ;;
     folder)
-      rm -f "$target/understand-anything"
+      [[ -L "$target/understand-anything" ]] && rm -f "$target/understand-anything"
       ;;
   esac
 }
@@ -186,18 +199,16 @@ cmd_uninstall() {
   target="$(printf '%s\n' "$row" | cut -d'|' -f2)"
   style="$(printf '%s\n' "$row" | cut -d'|' -f3)"
 
-  if [[ ! -d "$REPO_DIR" ]]; then
-    printf 'No checkout found at %s — nothing to unlink.\n' "$REPO_DIR"
-    exit 0
-  fi
   printf -- '→ Removing skill links for %s\n' "$id"
   unlink_skills "$target" "$style"
   if [[ -L "$PLUGIN_LINK" ]]; then
     rm -f "$PLUGIN_LINK"
     printf '  ✓ removed %s\n' "$PLUGIN_LINK"
   fi
-  printf '\nThe checkout at %s was kept (other platforms may still use it).\n' "$REPO_DIR"
-  printf 'To remove it: rm -rf "%s"\n' "$REPO_DIR"
+  if [[ -d "$REPO_DIR" ]]; then
+    printf '\nThe checkout at %s was kept (other platforms may still use it).\n' "$REPO_DIR"
+    printf 'To remove it: rm -rf "%s"\n' "$REPO_DIR"
+  fi
 }
 
 cmd_update() {