fix(ci): shut down MSBuild build-server before restore and build

[KiarashMinoo]

User description

Summary

• pack-solution.ps1 runs Clean, Restore, and Build as three separate dotnet invocations, but the .NET SDK keeps a persistent MSBuild/VBCSCompiler server warm across them by default.
• If Clean deletes files that a consumer's own Directory.Build.props-style targets manage (e.g. downloading shared config into a gitignored scratch folder on a BeforeTargets="Restore" hook), that warm server can serve the following Restore call a stale "nothing to restore" evaluation from before those targets had anything to fetch — silently skipping them and leaving Build to fail on missing package/property state that never actually gets (re)downloaded.
• This showed up as a real CI failure in ThunderPropagator (BuildingBlocks/Ardalis/CaseConverter type-not-found cascade on ThunderPropagator.Application), and reproduces the exact same failure signature I confirmed and root-caused separately this session for the local dotnet restore/dotnet build-server staleness bug.
• Adds dotnet build-server shutdown immediately before Restore and before Build, forcing a cold, disk-accurate evaluation each time. This is a no-op when the staleness bug isn't in play, so it's safe for every consumer of this script.

Caveat: I could not reproduce the exact CI failure locally on a single clean run — my working theory is that the staleness compounds across the workflow-level retry loop (an initial attempt hits an unrelated transient blip, but the warm server surviving into the retry then causes the real no-op-restore failure). The fix addresses the confirmed staleness bug class regardless, but isn't a 100%-proven root cause for this specific incident.

Test plan

• Validated PowerShell syntax of the edited script
• Confirmed main branch protection requires a PR (no direct push)
• Re-run ThunderPropagator's CI to confirm the fix resolves the observed failure

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PR Type

Bug fix

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Description

• Add build-server shutdown before restore

• Add build-server shutdown before build

• Prevent stale restore evaluation

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Diagram Walkthrough

flowchart LR
  Clean["Clean"] --> SR["Shutdown before Restore"]
  SR --> Restore["Restore"]
  Restore --> SB["Shutdown before Build"]
  SB --> Build["Build"]

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File Walkthrough

	Relevant files
Bug fix	pack-solution.ps1 Add build-server shutdown before restore and build              .github/scripts/pack-solution.ps1 Insert dotnet build-server shutdown before restore Insert dotnet build-server shutdown before build Add explanatory comments about server staleness +15/-2

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[github-actions]

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