Fix install scripts and add .NET runtime requirement documentation (#69)

* Fix bash install script line endings and JSON parsing

- Convert Windows CRLF line endings to Unix LF format
- Redirect log output to stderr to prevent JSON corruption
- Fix JSON parsing for single-line GitHub API responses
- Update download URL extraction to handle compact JSON format

* Fix PowerShell install script PATH variable syntax

- Use ${InstallPath} syntax to properly escape colon in PATH export
- Add file existence check before reading shell profile
- Fix pattern matching for existing PATH entry detection

* Add .NET runtime requirement documentation and checks

- Add Prerequisites section to README explaining .NET 9 Runtime requirement
- Add runtime detection to both install scripts with user warnings
- Simplify installation instructions with one-liner commands
- Move advanced install options to collapsible details section

Author: Aaronontheweb

README.md

@@ -35,31 +35,46 @@ link-validator --url https://example.com --output new-sitemap.md --diff old-site
 
 ## 📦 Installation
 
+### Prerequisites
+
+**Required:** [.NET 9 Runtime](https://dotnet.microsoft.com/download/dotnet/9.0) must be installed on your system to run LinkValidator.
+
+- **Windows:** Download the [.NET 9 Runtime](https://dotnet.microsoft.com/download/dotnet/9.0/runtime)
+- **Linux/macOS:** Install via package manager or download from [Microsoft](https://dotnet.microsoft.com/download/dotnet/9.0)
+
 ### Option 1: Install Script (Recommended)
 
 **Windows (PowerShell):**
 ```powershell
-# Install to default location and add to PATH
 irm https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.ps1 | iex
+```
 
+**Linux/macOS (Bash):**
+```bash
+curl -fsSL https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.sh | bash
+```
+
+<details>
+<summary>Advanced installation options</summary>
+
+**Windows custom options:**
+```powershell
 # Install to custom location  
 irm https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.ps1 | iex -ArgumentList "-InstallPath", "C:\tools\linkvalidator"
 
 # Install without adding to PATH
 irm https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.ps1 | iex -ArgumentList "-SkipPath"
 ```
 
-**Linux/macOS (Bash):**
+**Linux/macOS custom options:**
 ```bash
-# Install to default location and add to PATH
-curl -fsSL https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.sh | bash
-
 # Install to custom location
 curl -fsSL https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.sh | bash -s -- --dir ~/.local/bin
 
 # Install without adding to PATH
 curl -fsSL https://raw.githubusercontent.com/Aaronontheweb/link-validator/dev/install.sh | bash -s -- --skip-path
 ```
+</details>
 
 ### Option 2: Download Binary
 
@@ -72,6 +87,8 @@ Download the appropriate binary from the [latest release](https://github.com/Aar
 
 Extract and place the binary in your PATH.
 
+**Note:** These binaries require the .NET 9 Runtime to be installed (see Prerequisites above).
+
 ### Option 3: Build from Source
 
 **Prerequisites:** [.NET 9 SDK](https://dotnet.microsoft.com/download)

install.ps1

@@ -74,6 +74,16 @@ Write-Host "LinkValidator Installer" -ForegroundColor Green
 Write-Host "Platform: $Platform-$Architecture" -ForegroundColor Cyan
 Write-Host "Install Path: $InstallPath" -ForegroundColor Cyan
 
+# Check for .NET runtime
+try {
+    $null = & dotnet --version 2>$null
+} catch {
+    Write-Host "`nWARNING: .NET runtime not detected!" -ForegroundColor Yellow
+    Write-Host "LinkValidator requires .NET 9 Runtime to run." -ForegroundColor Yellow
+    Write-Host "Download from: https://dotnet.microsoft.com/download/dotnet/9.0" -ForegroundColor Yellow
+    Write-Host "Continuing with installation...`n" -ForegroundColor Cyan
+}
+
 # Get latest release info or specific version
 if ($Version) {
     $ReleaseUrl = "$GITHUB_API_URL/releases/tags/$Version"
@@ -163,9 +173,9 @@ try {
                                elseif (Test-Path ~/.bashrc) { "~/.bashrc" } 
                                else { "~/.profile" }
 
-                $PathLine = "export PATH=`"$InstallPath:\`$PATH`""
+                $PathLine = "export PATH=`"${InstallPath}:\`$PATH`""
 
-                if (-not (Get-Content $ShellProfile -ErrorAction SilentlyContinue | Select-String -Pattern [regex]::Escape($InstallPath))) {
+                if (-not (Test-Path $ShellProfile) -or -not (Get-Content $ShellProfile -ErrorAction SilentlyContinue | Select-String -Pattern ([regex]::Escape($InstallPath)))) {
                     Add-Content -Path $ShellProfile -Value $PathLine
                     Write-Host "✓ Added to $ShellProfile. Run 'source $ShellProfile' or restart your terminal." -ForegroundColor Green
                 } else {