[Bug]: SQL Database Projects extension should not require NuGet access at build time

[ssreerama]

Description

SQL Database Projects extension v1.5.7 attempts to download build-time dependencies from nuget.org during project build:

Microsoft.Build.Sql/2.0.0
Microsoft.SqlServer.TransactSql.ScriptDom/170.128.0

If the environment cannot access nuget.org (proxy, restricted, allowlisted, or air-gapped), the extension fails to build and “won’t proceed,” even though older versions (<= 1.5.6) were usable in these environments. Rolling back to 1.5.6 restores build capability. [learn.microsoft.com]
This is a major enterprise/government blocker: extensions must be deterministic and not depend on live, post-install downloads to function.

Steps to Reproduce

1. In a network-restricted environment (or simulate by blocking nuget.org), install:
   ms-mssql.sql-database-projects-vscode v1.5.7
2. Open any SQL project and run Build.
3. Observe extension output:

• Attempts to download Microsoft.Build.Sql.2.0.0 from nuget.org
• Attempts to download Microsoft.SqlServer.TransactSql.ScriptDom.170.128.0 from nuget.org
• Fails with “Download error” and build does not proceed.

Affected Area

• Connection dialog (SQL Server | Azure browse/Fabric browse)
• Query editor
• Query results panel
• Object Explorer
• GitHub Copilot integration
• Preview/Edit data
• Table Designer
• Schema Designer
• Schema Compare
• Local SQL Server Container provisioning
• SQL database in Fabric provisioning
• DACPAC/BACPAC export/import
• SQL Database projects
• Query Plan Visualizer
• Other (please describe below)

If you selected "Other", please describe the affected area

No response

Environment Information

sqlproj - 1.5.7
mssql - 1.40.0

Confirmation

• I have searched existing issues and couldn't find a match
• I want to work on this issue

[ssreerama]

#21357