fix: pass 'indexes' invokeSource for MSSQL filtered index WHERE clause

[funsaized]

Summary

Fixes #5593

When defining a filtered unique index with where(isNotNull(...)) for SQL Server, drizzle-kit generates a fully qualified column name (e.g., [schema].[table].[column]) inside the WHERE clause, which SQL Server rejects for filtered indexes.

Root Cause

In drizzle-kit/src/dialects/mssql/drizzle.ts, the where clause for indexes was serialized without passing the 'indexes' invokeSource to dialect.sqlToQuery():

// Before (bug):
let where = index.config.where ? dialect.sqlToQuery(index.config.where).sql : '';

// After (fix):
let where = index.config.where ? dialect.sqlToQuery(index.config.where, 'indexes').sql : '';

Without 'indexes', column references in the WHERE clause get fully qualified as [schema].[table].[column]. The core SQL serializer in drizzle-orm/src/sql/sql.ts already has handling for invokeSource === 'indexes' — when set, it returns just the column name [column], which is valid T-SQL for filtered indexes.

This matches how the Postgres dialect already handles index WHERE clauses (passing 'indexes' to sqlToQuery).

Changes

• drizzle-kit/src/dialects/mssql/drizzle.ts: Pass 'indexes' as invokeSource when serializing the WHERE clause
• drizzle-kit/tests/mssql/indexes.test.ts: Update test expectations to match the unqualified column names
• drizzle-kit/tests/mssql/tables.test.ts: Update test expectations to match the unqualified column names

Before / After

Before (invalid T-SQL):

CREATE UNIQUE INDEX [users_employee_id_idx]
ON [user_schema].[users] ([employee_id])
WHERE ([user_schema].[users].[employee_id] is not null);

After (valid T-SQL):

CREATE UNIQUE INDEX [users_employee_id_idx]
ON [user_schema].[users] ([employee_id])
WHERE ([employee_id] is not null);