feat: add startup config validation and document ConfigManager pipeline editor

Add ConfigurationValidationRunner with IConfigurationValidator interface for
validating required settings at startup. Includes SecureStore and LDAP validators.
Expand ConfigManager with pipeline editing UI, dialogs, and step editors.
Update documentation with config validation guidance.

CLAUDE.md

@@ -11,11 +11,25 @@ This is a **migration project** to convert a legacy .NET Framework 4.8 applicati
 JdeScopingTool/
 ├── OLD/            # Legacy .NET Framework 4.8 source code (read-only reference)
 ├── NEW/            # New .NET 10 solution (build here)
+│   └── JdeScoping.slnx   # Solution file (.slnx format)
 ├── openspec/       # OpenSpec specifications and design documents
 ├── PLANS/          # Design plans, implementation plans, and task lists
 └── DOCUMENTATION/  # Project documentation
 ```
 
+### Build Commands
+The solution uses the `.slnx` format (XML-based solution file):
+```bash
+# Build entire solution
+dotnet build NEW/JdeScoping.slnx
+
+# Run all tests
+dotnet test NEW/JdeScoping.slnx
+
+# Build specific project
+dotnet build NEW/src/JdeScoping.Host/JdeScoping.Host.csproj
+```
+
 ### Legacy System Purpose
 A manufacturing/ERP search tool that:
 - Caches data from JDE (JD Edwards - Oracle) and CMS (Sybase) enterprise systems into SQL Server