fix(windows): move -ExecutionPolicy Bypass before -c in uninstall command

The -ExecutionPolicy Bypass flag was placed after the -c argument in the
registry UninstallString, causing PowerShell to treat it as part of the
command text rather than as a PowerShell option. This made uninstalling
Bun fail on Windows systems with Restricted or AllSigned execution
policies. Also adds the flag to the documented uninstall command.

Closes #27399

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

docs/installation.mdx

@@ -344,7 +344,7 @@ To remove Bun from your system:
 
     <Tab title="Windows">
     	```powershell PowerShell icon="windows"
-    powershell -c ~\.bun\uninstall.ps1
+    powershell -ExecutionPolicy Bypass -c ~\.bun\uninstall.ps1
     ```
     </Tab>
 

src/cli/install.ps1

@@ -287,7 +287,7 @@ function Install-Bun {
       New-ItemProperty -Path $RegistryKey -Name "DisplayName" -Value "Bun" -PropertyType String -Force | Out-Null
       New-ItemProperty -Path $RegistryKey -Name "InstallLocation" -Value "${BunRoot}" -PropertyType String -Force | Out-Null
       New-ItemProperty -Path $RegistryKey -Name "DisplayIcon" -Value $BunBin\bun.exe -PropertyType String -Force | Out-Null
-      New-ItemProperty -Path $RegistryKey -Name "UninstallString" -Value "powershell -c `"& `'$BunRoot\uninstall.ps1`' -PauseOnError`" -ExecutionPolicy Bypass" -PropertyType String -Force | Out-Null
+      New-ItemProperty -Path $RegistryKey -Name "UninstallString" -Value "powershell -ExecutionPolicy Bypass -c `"& `'$BunRoot\uninstall.ps1`' -PauseOnError`"" -PropertyType String -Force | Out-Null
     } catch {
       if ($rootKey -ne $null) {
         Remove-Item -Path $RegistryKey -Force