Add Explorer Workbench with hierarchical, off-UI Storage analysis.

Storage queries run in the background with cancellation and covering indexes so switching views no longer freezes the UI.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

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+## Build
+bin/
+obj/
+[Bb]uild/
+[Ll]og/
+*.user
+*.suo
+*.userosscache
+*.sln.docstates
+*.vs/
+.vs/
+[Dd]ebug/
+[Rr]elease/
+x64/
+x86/
+[Aa]rtifacts/
+TestResults/
+*.trx
+*.coverage
+*.nupkg
+project.lock.json
+
+## IDE
+.idea/
+*.DotSettings.user
+*.rsuser
+
+## OS
+Thumbs.db
+Desktop.ini
+.DS_Store
+
+## App local (never commit a user's index)
+*.db
+*.db-shm
+*.db-wal
+*.log