Delete leftover empty ComparisonTool.* directories at repository root

[tayzer]

Summary

Ten ComparisonTool.* directories remain at the repository root, left over from the V1→V2 rename. They contain no tracked files — only ignored bin/, obj/, and one stray .csproj.user. git status is clean because everything inside them is gitignored, so they are invisible in review but very visible to anyone browsing the working tree.

ComparisonTool.Cli/                  non-build files: 0
ComparisonTool.Core/                 non-build files: 0
ComparisonTool.Desktop/              non-build files: 0
ComparisonTool.Domain/               non-build files: 0
ComparisonTool.MockApi/              non-build files: 0
ComparisonTool.Report/               non-build files: 0
ComparisonTool.TestDataGenerator/    non-build files: 0
ComparisonTool.Tests/                non-build files: 0
ComparisonTool.UI/                   non-build files: 0
ComparisonTool.Web/                  non-build files: 1  (ComparisonTool.Web.csproj.user)

Why it matters

A newcomer cloning the repo and opening the root sees ComparisonTool.Core/ next to Source/ and Tests/ and reasonably concludes there are two codebases. The actual V1 code is at archive/v1-comparisontool/, and these directories are unrelated to it — they are just build output whose source projects were moved.

They also make root-level find/grep noisier than it needs to be, and stale obj/ folders with old project names can confuse IDE project discovery.

Fix

Delete all ten. Nothing tracked is lost:

git clean -nxd ComparisonTool.*    # review first

The single ComparisonTool.Web/ComparisonTool.Web.csproj.user is a local IDE preferences file for a project that no longer exists — safe to discard.

Worth confirming afterwards that no script, .sln, launch config, or CI workflow references these paths. A grep for ComparisonTool.Core, ComparisonTool.UI etc. outside archive/ should come back empty except for ComparisonTool.sln itself, which is the solution filename and stays as-is.