Add net11 support, CSDL LongDescription, and isolate EF tests

[robertmclaws]

This brings dev up to main with .NET 11 support, CSDL LongDescription handling, docs fixes, and test isolation.

.NET 11

• Pin the SDK to 11.0.100-rc.1 (roll-forward latest feature, prerelease allowed) in global.json / src/global.json.
• Add net11.0 to StandardTestTfms and treat net8+ as IsNetCore.
• Keep per-TFM package groups; float 11.x as 11.*-* / [11.*-*, 12.0.0).
• Drop coverlet.collector; floor test System.Text.Json at 10.x (11.x on net11) so MSTest 4.4 CodeCoverage restores.
• Stub DirectUpdate / DirectDelete (sync and async) on EF Core net11 — Z.EntityFramework.Plus has no 11.x package yet; the methods log a console warning and return 0.
• Follow-up: Z.EntityFramework.EF6 package reference update.

CSDL documentation

• CodeGen maps CSDL Summary → /// <summary> and LongDescription → /// <remarks>; empty docs emit no XML comment block.
• EF Core → EDMX writes CSDL LongDescription (not SSDL).
• New EasyAFLongDescription path: one SQL round-trip of sys.extended_properties named EasyAF_LongDescription, then in-memory apply to the CSDL model (preserve existing docs when the catalog has no value).
• CodeGen entity/DbContext baselines updated to match (no empty summary stubs).

Tests

• Round Interval expected values to 8 decimals so net11 Convert.ToDecimal(double) (correctly rounded binary floats) still matches.
• Remove WriteSimpleMessageBusFiles; CodeGen tests compare against checked-in baselines. Baseline refresh stays on [BreakdanceManifestGenerator].
• [DoNotParallelize] on EF database tests; EntityManagerTests assert and clean up only the rows they created instead of the whole Products table.
• ApiClientTests host configuration updated for the current ConfigureServices signature.

Docs

• Docs site content/escaping fixes and docs.json update.