feat: typed constraint errors (unique, not-null, fk, check)

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/claim #376
Fixes #376

feat: typed constraint errors across pg, mysql, sqlite, and singlestore

This builds on the typed-error hierarchy explored in #5383 and keeps its public class names, while completing SingleStore wiring, repo-standard is() support, delete-side MySQL FK errors, and safe handling of non-Error throws.

Catching a unique-violation today means parsing driver-specific code / errno / message strings. This wraps those into one typed instanceof / is() chain that still keeps the original driver error on .cause.

try {
  await db.insert(users).values({ email });
} catch (e) {
  if (e instanceof UniqueConstraintViolationError) {
    e.constraintName; // 'users_email_key'
    e.table;          // 'users'
    e.cause;          // original pg/mysql2/libsql error
  }
}

DrizzleQueryError keeps the same behavior for everything that is not a constraint failure (syntax, connection, missing relation, …). Additive — no existing catch of DrizzleQueryError breaks.

Mapping

	unique	not null	foreign key	check
Postgres	23505	23502	23503	23514
MySQL / SingleStore	1062	1048	1451/1452/1216/1217	3819
SQLite	SQLITE_CONSTRAINT_UNIQUE / PRIMARYKEY + libsql message	NOTNULL	FOREIGNKEY	CHECK

Wired in the one place every driver already goes through: queryWithCache in pg-core, mysql-core, sqlite-core, and singlestore-core.

Classes are exported from drizzle-orm (export * from './errors.ts' already).

Related open work

PR	Difference
#3996	WIP since May 2025; covers broader debugging/logging and currently only postgres.js
#5383	Typed-error foundation used here; this PR adds SingleStore, Drizzle is(), complete MySQL FK extraction/delete codes, and non-Error safety
#6064	Postgres-only; its synchronous try/catch around a thenable does not cover async rejections
#5877	Also adds an onError hook and changes 68 files; broader, separate scope
#5412	Adds an onError callback rather than typed constraint classes

No onError hook in this PR. Constraint classes first; a hook can sit on top later.

Tests

drizzle-orm/tests/errors.test.ts — 22 cases, no live database: SQLSTATE, mysql errno (including FK table/column/constraint extraction), sqlite codes + libsql message fallback, unknown codes stay DrizzleQueryError, instanceof / is() behavior, and non-Error throws.