Admin Collections UI

Summary

The Admin app now treats document collections as first-class objects alongside tables, views, forms, and reports. The first implementation is a browser and JSON editor built on the existing collection client APIs:

• list collection names
• browse documents by page
• fetch one document by exact key
• create or update a document
• delete a document

This deliberately avoids new engine, HTTP, gRPC, or client contracts. Collection path-index management, document-content search, collection rename, and collection drop remain future work.

User Experience

• Object Explorer has a Collections filter chip and group.
• The collection group menu supports New Collection... and Refresh.
• Collection item menus support Open, New Document..., and Copy Name.
• The command palette includes New Collection plus one entry for each existing collection.
• Each collection opens in a dedicated collection:{name} tab using the same toolbar, pager, grid, and detail-panel language as table data tabs.

Collection Tab Behavior

• The grid shows row number, document key, JSON kind, and a compact preview.
• The detail panel shows indented JSON for the selected document.
• Existing document keys are read-only.
• New documents require a nonblank key and valid JSON before save is enabled.
• Save writes through PutDocumentAsync(collectionName, key, document).
• Delete writes through DeleteDocumentAsync(collectionName, key) after confirmation.
• Successful writes notify Admin change listeners and refresh the current page.
• Exact-key lookup uses GetDocumentAsync(collectionName, key).

Defaults

• Default page size is 25.
• Supported page sizes are 10, 25, 50, and 100.
• Collection names use the same simple identifier shape as the direct client: ^[A-Za-z_][A-Za-z0-9_]*$.
• Deleting all documents leaves the collection itself in place because there is no drop-collection API today.
• Generated collection model metadata is not surfaced; documents are edited as raw JSON.

Verification

Run the focused Admin checks after collection UI changes:

dotnet build src/CSharpDB.Admin/CSharpDB.Admin.csproj
dotnet test tests/CSharpDB.Admin.Forms.Tests/CSharpDB.Admin.Forms.Tests.csproj