P0: Web.config Custom Control Registry Parser

[csharpfritz]

Priority: P0 (Foundation)

Problem

The CLI migration pipeline ignores Web.config registrations of custom controls. This blocks prescan from detecting ASCX files and custom assemblies.

Scope

• Parse Web.config and sections
• Extract assembly registrations and namespace tags
• Integrate with RuntimeDetector for prescan reporting

Deliverables

1. WebConfigAssemblyParser class in src/BlazorWebFormsComponents.Cli/Analysis/
2. Integration into RuntimeDetector
3. Prescan output includes 'Custom Controls Found' section
4. Unit tests: tests/BlazorWebFormsComponents.Cli.Tests/Analysis/WebConfigAssemblyParserTests.cs
5. Integration test with WingtipToys/ContosoUniversity prescan

Acceptance Criteria

✅ Parser correctly extracts assembly/namespace from Web.config
✅ Prescan lists detected custom controls
✅ No crash on missing/malformed Web.config
✅ Unit tests pass
✅ Prescan works on WingtipToys and ContosoUniversity

Related Track Document

See dev-docs/control-migration/track-webconfig-parser.md