Fix dotnet new to suggest @ instead of deprecated :: separator in update notifications

[Copilot]

Fix deprecated :: separator in dotnet new update suggestions

This PR fixes the issue where dotnet new <sometemplate> suggests using the deprecated package::version syntax instead of the correct package@version syntax when advising about available upgrades.

Changes Completed:

• Update TemplatePackageDisplay.cs DisplayUpdateCheckResult method (line 50, 58)
• Update TemplatePackageCoordinator.cs DisplayUpdateCheckResult method (line 148, 156)
• Update TemplatePackageDisplay.cs DisplayUpdateCheckResults method (line 306, 311)
• Update TemplatePackageCoordinator.cs DisplayUpdateCheckResults method (line 847, 852)
• Update other display strings that show package::version format (lines 71, 169, 318, 474, 636)
• Update tests in DotnetNewUpdateTests.cs to validate the @ separator is used in suggestions
• Build and verify changes compile successfully
• All 20 integration tests for dotnet new update functionality pass
• Fix approval tests for built-in package install scenarios
• Fix InstallRequest.DisplayName usage to replace :: with @
• Fix TemplatePackage.DisplayName usage in success messages

Files Changed:

1. src/Cli/Microsoft.TemplateEngine.Cli/TemplatePackageDisplay.cs (12 changes)
2. src/Cli/Microsoft.TemplateEngine.Cli/TemplatePackageCoordinator.cs (18 changes)
3. test/dotnet-new.IntegrationTests/DotnetNewUpdateTests.cs (24 changes)
4. test/dotnet-new.IntegrationTests/DotnetNewInstallTests.Approval.cs (3 changes)
5. test/dotnet-new.IntegrationTests/DotnetNewInstantiateTests.Approval.cs (2 changes)
6. test/dotnet-new.IntegrationTests/Approvals/*.verified.txt (4 approval files updated)

Summary:

The fix replaces all occurrences of :: with @ in package version display strings and command suggestions throughout the template engine CLI. This includes:

• Update check notifications (single and bulk)
• Built-in package availability warnings
• Install request display names
• Force command suggestions
• Success messages after installation

Example output (before):

An update for template package 'Aspire.ProjectTemplates::9.4.0' is available.
To update the package use:
   dotnet new install Aspire.ProjectTemplates::9.5.0

Example output (after):

An update for template package '[email protected]' is available.
To update the package use:
   dotnet new install [email protected]

Testing:

✅ All 20 DotnetNewUpdateTests integration tests pass
✅ All 4 built-in package approval tests pass:

• CanShowWarningIfPackageIsAvailableFromBuiltInSources
• CanInstallPackageAvailableFromBuiltInsWithForce
• CannotInstallPackageAvailableFromBuiltIns
• CannotInstallMultiplePackageAvailableFromBuiltIns
  ✅ Manual testing confirms correct output
  ✅ Build succeeds with no warnings or errors

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[marcpopMSFT]

@copilot fix the templates tests that are failing because of the switch over from :: to @
CanShowWarningIfPackageIsAvailableFromBuiltInSources
CanInstallPackageAvailableFromBuiltInsWithForce
CannotInstallPackageAvailableFromBuiltIns
CannotInstallMultiplePackageAvailableFromBuiltIns

[Copilot]

@copilot fix the templates tests that are failing because of the switch over from :: to @
CanShowWarningIfPackageIsAvailableFromBuiltInSources
CanInstallPackageAvailableFromBuiltInsWithForce
...

Fixed in commit 5a2929d. All 4 approval tests now pass:

• CanShowWarningIfPackageIsAvailableFromBuiltInSources ✅
• CanInstallPackageAvailableFromBuiltInsWithForce ✅
• CannotInstallPackageAvailableFromBuiltIns ✅
• CannotInstallMultiplePackageAvailableFromBuiltIns ✅

The changes ensure that all DisplayName usages now show @ instead of :: for package versions, including:

• InstallRequest display names in package lists
• Force command suggestions
• Success messages after installation
• Updated test scrubbers and approval files