CLI: Add code-only server control scaffolder for DepartmentPortal-style controls

[csharpfritz]

Context

DepartmentPortal has 7 code-only server controls (no .ascx file) in samples/DepartmentPortal/Code/Controls/*.cs. These controls inherit from CompositeControl, DataBoundControl, Control, WebControl, and IPostBackEventHandler — they are pure C# server controls with no markup file.

The CLI pipeline currently only discovers .ascx user controls. Code-only controls in Code/Controls/ are entirely invisible to the migration pipeline. They are referenced in page markup via local:ControlName tag prefix (registered as a namespace-level tag prefix in Web.config) but no scaffolding is emitted for them.

Jeff's directive: "these should migrate directly with our shim control classes — we need a migration class in the CLI"

The 7 Code-Only Controls Found

Control	Base Class(es)	Used On
SectionPanel	Control, INamingContainer, [ParseChildren(true)], ITemplate props	Announcements.aspx (×1), Resources.aspx (×3)
EmployeeDataGrid	DataBoundControl (overrides PerformDataBinding + RenderContents)	Employees.aspx, Admin/ManageEmployees.aspx
EmployeeCard	CompositeControl (overrides CreateChildControls)	EmployeeDetail.aspx
PollQuestion	Control, IPostBackEventHandler (implements RaisePostBackEvent); uses Page.ClientScript.GetPostBackEventReference	Training.aspx
StarRating	WebControl (overrides RenderContents, TagKey)	EmployeeDetail.aspx
NotificationBell	WebControl; raises NotificationClicked / NotificationDismissed events	Defined only (not yet placed on a page)
DepartmentBreadcrumb	Control, IPostBackEventHandler; uses Page.ClientScript.GetPostBackEventReference	Defined only (not yet placed on a page)

Source Location

samples/DepartmentPortal/Code/Controls/

Proposed Approach

Create a CodeOnlyControlScaffolder class in src/BlazorWebFormsComponents.Cli/Scaffolding/ that:

1. Scans C# files under the source project for classes that inherit from WebControl, CompositeControl, DataBoundControl, or Control
2. Skips known System.Web framework types (only emits stubs for user-defined controls)
3. Emits a Blazor .razor + .razor.cs component stub pair for each discovered control
4. Maps Web Forms base classes to BWFC shim base classes:

Web Forms Base	BWFC Base Class
WebControl	BaseStyledComponent
CompositeControl	BaseWebFormsComponent
DataBoundControl	DataBoundComponent<T>
Control	BaseWebFormsComponent

5. Preserves public properties from the original class as [Parameter] properties in the emitted .razor.cs
6. Preserves public events from the original class as EventCallback or EventCallback<T> parameters

The scaffolder should run as part of the MigrationPipeline before markup transforms so that discovered controls are available when LocalTagNamespaceResolutionTransform (see companion issue) resolves local: tags.

Acceptance Criteria

• CLI discovers all 7 code-only controls in DepartmentPortal's Code/Controls/ folder
• A .razor + .razor.cs stub pair is emitted for each discovered control
• Each emitted stub compiles against its BWFC base class without errors
• Public properties from the original class are preserved as [Parameter] in the stub
• Public events from the original class are preserved as EventCallback or EventCallback<T> parameters
• Scaffolder is registered in MigrationPipeline and integrates with the LocalTagNamespaceResolutionTransform
• Tests added to tests/BlazorWebFormsComponents.Cli.Tests/

Notes

This is Tier 1 Critical Blocker P1 from the DepartmentPortal gap analysis. Without this, 7 controls used across multiple DepartmentPortal pages produce no output, and all local: markup references fail to resolve.