Razor component tag regex misses dotted-namespace components like My.Nested.Component

[Widthdom]

Summary

The Razor component tag regex captures only PascalCase non-dotted component names (e.g. <MyButton />). Real Blazor / Razor Components codebases routinely use dotted-namespace tags (e.g. <MyApp.Components.Forms.Button />) and these are not recognized as references to the underlying component type.

Evidence

• src/CodeIndex/Indexer/References/Languages/RazorReferenceExtractor.cs — RazorComponentTagRegex (around the file's component-detection helper, support code at line 627-681).

• Reproducer:

  @page "/"
  <MyApp.Components.Forms.LoginButton OnClick="HandleClick" />

  Index this file. The reference from the tag to MyApp.Components.Forms.LoginButton is missing or only the trailing segment is captured.

Impact

• references on a fully-qualified Razor component type under-reports usage sites in any project that doesn't use @using blanket imports.
• impact_analysis over a component is incomplete.

Proposed direction

• Extend RazorComponentTagRegex to allow [A-Za-z_][\w]*(?:\.[A-Za-z_][\w]*)* for the tag name.
• When emitting the reference, use the fully-qualified name as the target identifier.
• Add a unit test covering both single-segment and dotted-namespace component tags.

Repro env

• Branch: main @ 2ee912d (release v1.21.0)

[Widthdom]

Work started on branch fix-issue1440-1445-1479.