Support SQL Server in cluster SqlMessageStorage

[sbking]

Stacked on #6440; I'll rebase this PR after it merges.

Summary

SqlMessageStorage contains SQL Server-specific DDL and query paths, but adding an mssql leg to the existing storage suite exposes four SQL Server errors.

• omit the trailing FOR UPDATE, which is not valid T-SQL in these queries
• replace nullable UNIQUE constraints with filtered unique indexes so NULL message and reply keys keep the same semantics as the other dialects
• replace the deprecated TEXT columns with NVARCHAR(MAX) so NULL parameters can be inserted (error 206 otherwise)
• change the MERGE path to return inserted.id, then read the previous reply when no row was inserted, since SQL Server rejects subqueries in OUTPUT (error 10705)
• add a SQL Server testcontainer fixture, shared-suite coverage, migration tests, and a patch changeset

Fresh databases use the corrected DDL. An idempotent 0003_mssql_schema_fixes migration updates existing SQL Server schemas and is a no-op on other dialects. The shared suite gains a 30s describe timeout (as in test/fixtures/rpc-e2e.ts) because concurrent per-test migrations against the SQL Server container can exceed the 5s default.

Testing

• pnpm vitest run packages/platform-node/test/cluster/SqlMessageStorage.test.ts packages/platform-node/test/cluster/SqlMessageStorageMssql.test.ts (39/39 against SQL Server 2022; also green against SQL Server 2025)
• with only the test commit applied, the SQL Server leg fails 5/8 with errors 1003 and 2627 while PostgreSQL, MySQL, and SQLite pass 29/29
• pnpm check
• pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: 9ad877d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 27 packages

Name	Type
effect	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/vitest	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-pglite	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/openapi-generator	Patch

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