Dart modular_api_sqlserver hard-depends on dart_odbc, breaking the contracts-only stance

[ccisnedev]

Problem

modular_api_sqlserver (Dart) declares a hard runtime dependency on a driver, breaking the contracts-only stance that the other 5 db packages keep:

• code/dart/modular_api_sqlserver/pubspec.yaml:13 -> dart_odbc: ^6.2.0
• Used only by code/dart/modular_api_sqlserver/lib/src/sql_server_metadata_reader.dart (SqlServerMetadataReader, GraphQL Stage-1 schema introspection).

By contrast, TS and Python keep the equivalent SqlServerMetadataReader in the core and load the driver lazily (require('mssql') / dynamic import pyodbc), so their package manifests declare no driver and stay contracts-only. Dart cannot do lazy package loading (static imports, dep must be in pubspec), so the driver leaks into the manifest and every consumer of modular_api_sqlserver pulls dart_odbc even if they only want the DbClient contracts.

Fix direction (per the contracts-only vision, ADR-0004)

Remove the driver from the package — do NOT wrap it in a new satellite package (that adds packages and perpetuates the driver, the opposite of the goal). The metadata reader that needs a driver becomes the user's responsibility (like the db adapter), or ships as an example in docs. modular_api_sqlserver (and, longer term, a unified modular_api_sql) stays pure contracts.

Notes

• Breaking in Dart (the exported SqlServerMetadataReader symbol / import path goes away). No Dart consumers in production today.
• Minor related asymmetry to note: Dart modular_api_postgres has no metadata reader at all.
• Dedicated iteration — not to be mixed with feature work. Aligns with the longer-term goal of converging the 6 db packages into a single modular_api_sql per SDK.