Fix: Apply path validation to all custom paths with improved error message

Previously, the validation that checks if the install path is inside
`.claude/skills` or `.codex/skills` only ran when using `--path .` or
`--path current`. This meant arbitrary paths like `/tmp` could be used.

Now:
- Any custom path (including `.`, `current`, or absolute paths) is validated
- Error message clearly explains both valid options (default vs custom path)
- Shows examples of correct usage when validation fails

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ibrahimkteish

Sources/pfw/Install.swift

@@ -74,21 +74,34 @@ struct Install: AsyncParsableCommand {
 
     if isCurrentDirectory {
       installURL = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
+    } else {
+      installURL = URL(fileURLWithPath: path ?? tool.defaultInstallPath.path)
+    }
 
-      // Verify the current directory is in the expected location
-      let currentPath = installURL.path
+    // Verify the install path is in the expected location (only if custom path provided)
+    if path != nil {
+      let installPath = installURL.path
       let expectedPattern = ".\(tool.rawValue)/skills"
 
-      guard currentPath.contains(expectedPattern) else {
-        print("Error: Current directory is not in the expected location.")
-        print("Expected to be inside: ~/.\(tool.rawValue)/skills/")
-        print("Current directory: \(currentPath)")
+      guard installPath.contains(expectedPattern) else {
+        print("Error: Install path is not in the expected location.")
+        print("")
+        print("The install path must contain '.\(tool.rawValue)/skills' in it.")
+        print("")
+        print("Valid options:")
+        print("  1. Use default path: pfw install --tool \(tool.rawValue)")
+        print("     Installs to: ~/.\(tool.rawValue)/skills/the-point-free-way")
+        print("")
+        print("  2. Use custom path ending with '.\(tool.rawValue)/skills':")
+        print("     pfw install --tool \(tool.rawValue) --path /your/project/.\(tool.rawValue)/skills")
+        print("")
+        print("Current install path: \(installPath)")
         throw ExitCode.failure
       }
 
-      // Ask for confirmation
-      print("You are about to install into the current directory:")
-      print("  \(currentPath)")
+      // Ask for confirmation when using custom path
+      print("You are about to install into:")
+      print("  \(installPath)")
       print("\nThis will merge new skills with existing ones without removing current files.")
       print("Continue? (yes/no): ", terminator: "")
 
@@ -97,8 +110,6 @@ struct Install: AsyncParsableCommand {
         print("Installation cancelled.")
         throw ExitCode.success
       }
-    } else {
-      installURL = URL(fileURLWithPath: path ?? tool.defaultInstallPath.path)
     }
 
     // Always merge - never remove existing files