fix: Emit type-only imports in all driver preambles

Driver preambles imported types (QueryArrayConfig/QueryArrayResult from
pg, Sql from postgres, Database from better-sqlite3, mysql/RowDataPacket/
ResultSetHeader from mysql2) as value imports, which fails to compile
under `verbatimModuleSyntax` and forces the runtime driver package to be
a hard dependency of the generated module.

All preamble imports are now `import type`. The mysql2 default+named
import is split into two declarations because a type-only import cannot
combine a default import with named bindings.

Verified the generated output for all drivers compiles under
`tsc --strict` with `verbatimModuleSyntax: true`.

Fixes #55. Fixes #61.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GFyrFwpJC2eivaBRyNBJqv

Author: rtolsma

examples/bun-mysql2/src/db/query_sql.ts

@@ -1,6 +1,8 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import mysql, { RowDataPacket, ResultSetHeader } from "mysql2/promise";
+import type mysql from "mysql2/promise";
+
+import type { RowDataPacket, ResultSetHeader } from "mysql2/promise";
 
 type Client = mysql.Connection | mysql.Pool;
 

examples/bun-pg/src/db/query_sql.ts

@@ -1,6 +1,6 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import { QueryArrayConfig, QueryArrayResult } from "pg";
+import type { QueryArrayConfig, QueryArrayResult } from "pg";
 
 interface Client {
     query: (config: QueryArrayConfig) => Promise<QueryArrayResult>;

examples/bun-postgres/src/db/query_sql.ts

@@ -1,6 +1,6 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import { Sql } from "postgres";
+import type { Sql } from "postgres";
 
 export const getAuthorQuery = `-- name: GetAuthor :one
 SELECT id, name, bio FROM authors

examples/node-better-sqlite3/src/db/query_sql.ts

@@ -1,6 +1,6 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import { Database } from "better-sqlite3";
+import type { Database } from "better-sqlite3";
 
 export const getAuthorQuery = `-- name: GetAuthor :one
 SELECT id, name, bio FROM authors

examples/node-mysql2/src/db/query_sql.ts

@@ -1,6 +1,8 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import mysql, { RowDataPacket, ResultSetHeader } from "mysql2/promise";
+import type mysql from "mysql2/promise";
+
+import type { RowDataPacket, ResultSetHeader } from "mysql2/promise";
 
 type Client = mysql.Connection | mysql.Pool;
 

examples/node-pg/src/db/query_sql.ts

@@ -1,6 +1,6 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import { QueryArrayConfig, QueryArrayResult } from "pg";
+import type { QueryArrayConfig, QueryArrayResult } from "pg";
 
 interface Client {
     query: (config: QueryArrayConfig) => Promise<QueryArrayResult>;

examples/node-postgres/src/db/query_sql.ts

@@ -1,6 +1,6 @@
 // Code generated by sqlc. DO NOT EDIT.
 
-import { Sql } from "postgres";
+import type { Sql } from "postgres";
 
 export const getAuthorQuery = `-- name: GetAuthor :one
 SELECT id, name, bio FROM authors

src/drivers/better-sqlite3.ts

@@ -125,7 +125,7 @@ export class Driver {
       factory.createImportDeclaration(
         undefined,
         factory.createImportClause(
-          false,
+          true,
           undefined,
           factory.createNamedImports([
             factory.createImportSpecifier(

src/drivers/mysql2.ts

@@ -237,8 +237,18 @@ export class Driver {
       factory.createImportDeclaration(
         undefined,
         factory.createImportClause(
-          false,
+          true,
           factory.createIdentifier("mysql"),
+          undefined
+        ),
+        factory.createStringLiteral("mysql2/promise"),
+        undefined
+      ),
+      factory.createImportDeclaration(
+        undefined,
+        factory.createImportClause(
+          true,
+          undefined,
           factory.createNamedImports([
             factory.createImportSpecifier(
               false,

src/drivers/pg.ts

@@ -350,7 +350,7 @@ export class Driver {
       factory.createImportDeclaration(
         undefined,
         factory.createImportClause(
-          false,
+          true,
           undefined,
           factory.createNamedImports([
             factory.createImportSpecifier(
@@ -381,7 +381,7 @@ export class Driver {
         factory.createImportDeclaration(
           undefined,
           factory.createImportClause(
-            false,
+            true,
             undefined,
             factory.createNamedImports([
               factory.createImportSpecifier(