fix(sqlite,mysql): implement the non-generic Weasel.Core.ICommandBuilder

[jeremydmiller]

Fixes #423.

Weasel.Sqlite.CommandBuilder and Weasel.MySql.CommandBuilder derive from CommandBuilderBase<,,> but never declared the non-generic Weasel.Core.ICommandBuilder, so nothing targeting the neutral contract could be handed one.

That contract is what every Weasel.Storage closed-shape operation configures itself against:

void ConfigureCommand(ICommandBuilder builder, IStorageSession session);

so the practical effect was that no Weasel.Storage document or event operation could execute against SQLite at all — there was no way to construct the builder argument. Found while building Fisher on Weasel.Storage.

Postgresql, SqlServer and Oracle already carry the interface; Sqlite and MySql were the two left behind by #327. Only SQLite was blocking a consumer today, but MySql had the identical gap and would hit it the moment a Weasel.Storage consumer targeted it, so both are fixed here.

Missing members

Four on each provider — everything else the interface needs was already inherited from CommandBuilderBase:

Member	Before
string TenantId { get; set; }	absent
void AppendParameters(params object[])	absent
DbParameter AppendParameter(object)	absent — the inherited overloads all return void, so none satisfied the interface
IGroupedParameterBuilder CreateGroupedParameterBuilder(char?)	absent

Two deliberate choices

AppendParameter / AppendParameters are implemented explicitly, following Weasel.Oracle rather than Weasel.SqlServer. The base class already exposes void-returning AppendParameter overloads; a public member would hide them and silently change which overload existing call sites bind to. Explicit implementation adds the interface without touching the public surface, so this is additive for existing users.

StartNewCommand is not overridden. Weasel.SqlServer overrides it to a no-op, but the base is already a no-op ("multi-statement providers just keep appending"), which is correct for both of these — Microsoft.Data.Sqlite and MySqlConnector both execute several semicolon-separated statements from one command. An override would be noise implying a difference that does not exist.

Tests

A contract test per provider covering the interface itself plus each of the four members, so the set cannot drift again:

• src/Weasel.Sqlite.Tests/CommandBuilderTests.cs — CommandBuilderNeutralContractTests
• src/Weasel.MySql.Tests/CommandBuilderNeutralContractTests.cs

Both are pure type/behaviour tests needing no database server.

Verification

• Full Weasel.slnx builds clean.
• Weasel.Sqlite.Tests: 393 passed, 0 failed, on net9.0 and net10.0.
• Weasel.MySql.Tests CommandBuilderNeutralContractTests: 6 passed (the rest of that suite needs a MySQL server and was not run).

Fisher currently carries a local FisherCommandBuilder shim and will delete it once this ships.