[electricessence]

The rc.4 deprecations (API shape): members with a better route get [Obsolete] as a warning, never an error. Every message names the exact replacement, never points at another obsolete member, and ends "Removed in 12." like the existing ones.

Merge after #117. Several messages name reader.Map(...) and command.Map(...), which #117 adds. They are named in plain text only (no cref), so this branch builds on its own.

Marked

• IDataReader ToList/ToArray/ToImmutableArray(transform) and the sync-transform DbDataReader.ToListAsync(transform) → reader.Map(transform).ToList() and its siblings (ToListAsync(cancellationToken) for the async one). Select and SelectAsync stay, and so does the ValueTask-transform ToListAsync.
• IExecuteReader ToList/ToArray/ToImmutableArray(transform, behavior) and IterateReader<TEntity, TResult> → .Map(transform).ToList() / .Map(transform).Read(selector); for a non-default CommandBehavior, the ExecuteReader(handler, behavior) form. The IDbCommand IterateReader overloads stay.
• The three DbCommand sync-transform ToListAsync → command.Map(transform).ToListAsync(cancellationToken); for a CommandBehavior (or useReadAsync: false), the ExecuteReaderAsync(handler, behavior, cancellationToken) form.
• To<T>(DataTable, map, clearSourceTable), Transformer<T>.Results(DataTable, bool) and the rewritten ResultsFromDataTable message → table.CreateDataReader().Map(map).ToList(), then clear the table yourself.
• The four token-first MappedQueryExtensions.ReadAsync → the token-last ReadAsync(handler, cancellationToken).
• Every public type of the SqlClient package → Open.Database.Extensions.MSSqlClient (Microsoft.Data.SqlClient), which has the same API.
• AddParameterType(this IDbCommand, string, SqlDbType) in both SQL packages → AddParameterType on the SqlCommand.
• The protected ExpressiveCommandBase.Concat<T> → remaining is null ? [first] : remaining.Prepend(first).

Not marked in this PR (kept for now): items 15, 18 and 19 of the rc.4 list.

Library

• No library code calls a newly obsolete member except where one obsolete member forwards to another, under a scoped #pragma with a one-line reason; the rest now calls the non-obsolete implementation.
• PublicAPI files are unchanged (an [Obsolete] attribute does not change the API lines).

Docs and tests

• whats-new-11.md lists every newly deprecated member with its replacement; the foundation and mapping articles are updated.
• Tests that still call these members suppress CS0618 per call, with a reason; the deprecation tests cover the new members.
• Follow-up after rc.4: Map<T>() on a reader or a raw command (MappedReader<T>, MappedCommand<T>) #117 merges: the "after" sample for ResultsFromDataTable and one test replacement still use To<T>(DataTable) (under a pragma), because reader.Map is not on this branch yet. They move to CreateDataReader().Map(map).ToList() then.

Checks

• Release and Debug builds: 0 warnings, 0 errors. Tests: 9455 of 9455 pass in both. Samples: 96 of 96 checks pass. Style and analyzers: 0 findings. DocFX: 0 warnings.

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