Add ASPIREEXPORT001-010 diagnostics articles for Polyglot support

[Copilot]

Summary

Adds 10 new diagnostics articles for the ASPIREEXPORT series introduced in Aspire 13.2 as part of Polyglot (multi-language AppHost) support. These diagnostics are emitted by the new AspireExportAnalyzer in Aspire.Hosting.Integration.Analyzers.

The ASPIREATS001 article was already present in the repo.

New diagnostic articles

ID	Severity	Description
ASPIREEXPORT001	Error	[AspireExport] method must be static
ASPIREEXPORT002	Error	Invalid export ID format (must match [a-zA-Z][a-zA-Z0-9.]*)
ASPIREEXPORT003	Error	Return type is not ATS-compatible
ASPIREEXPORT004	Error	Parameter type is not ATS-compatible
ASPIREEXPORT005	Warning	[AspireUnion] requires at least 2 types
ASPIREEXPORT006	Warning	Union type is not ATS-compatible
ASPIREEXPORT007	Warning	Duplicate export ID for the same target type
ASPIREEXPORT008	Warning	Public extension method on exported type missing [AspireExport] or [AspireExportIgnore]
ASPIREEXPORT009	Warning	Export name may collide with other integrations
ASPIREEXPORT010	Warning	Synchronous callback invoked inline — may deadlock in multi-language app hosts

Changes

• Created 10 new MDX files in src/frontend/src/content/docs/diagnostics/
• Updated overview.mdx to include all 10 new diagnostics in the master table
• Updated reference.topics.ts sidebar: ASPIREEXPORT001–004 in Errors section, ASPIREEXPORT005–010 in Warnings section
• Verified all pages render correctly (HTTP 200) via local dev server

Related

• Analyzer source: https://github.com/dotnet/aspire/tree/release/13.2/src/Aspire.Hosting.Integration.Analyzers