improve sql errors (#1812)

Author: tim-smart

.changeset/consolidate-sql-error.md

@@ -0,0 +1,16 @@
+---
+"effect": 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-sqlite-bun": patch
+"@effect/sql-sqlite-do": patch
+"@effect/sql-sqlite-node": patch
+"@effect/sql-sqlite-react-native": patch
+"@effect/sql-sqlite-wasm": patch
+---
+
+Consolidate the SqlError changes to the new reason-based shape across effect and the SQL drivers, classifying native failures into structured reasons with Unknown fallback where native codes are unavailable.

.specs/README.md

@@ -22,3 +22,4 @@ This directory contains specifications for all major features and enhancements i
 - [revert-option-unboxing.md](revert-option-unboxing.md) - Revert APIs from `A | undefined` back to `Option<A>` across effect, cluster, cli, and platform packages.
 - [response-id-tracking.md](response-id-tracking.md) - Add per-client response ID tracking with `prepareUnsafe` method for incremental input mode in OpenAI providers.
 - [ai-embedding-model.md](ai-embedding-model.md) - Add `EmbeddingModel` module to `effect/unstable/ai` with batching via `RequestResolver` and telemetry.
+- [sql-error-reason-pattern.md](sql-error-reason-pattern.md) - Refactor SqlError to use the reason pattern with per-reason classes and best-effort error classification across all SQL drivers.