- Add provider contract (src/providers/provider.js): query() -> {rows,
rowsAffected, insertId}, callback transaction(fn), exec() for stored
procs, initialize/purge lifecycle
- Add MssqlProvider (src/providers/mssql/index.js) wrapping an mssql
ConnectionPool with normalized results, tx commit/rollback and
constraint-error classifiers (unique 2627/2601, FK 547)
- LibDashStore constructor now takes a provider instead of a pool
(breaking); adds LibDashStore.create() async factory; keeps pool as
transitional bridge until store modules are converted (see TODO.md)
- Move MSSQL-specific code into the provider: src/sql/* ->
src/providers/mssql/queries/*, src/schema.js ->
src/providers/mssql/schema.js, purge SQL -> purgeSql.js
- Update scripts, generate-schema-graph.js and package.json exports
(./providers/mssql, ./providers/provider)
- Add TODO.md with the remaining provider/SQLite migration plan
No SQL or behavioral changes.