feat: Add types_only option to generate interfaces without queries

With `types_only: true`, output contains only the Args/Row interfaces,
enum literal union types, and override imports — no driver imports,
query constants, or query functions. This lets a frontend share the
database types generated for a backend without pulling in a database
driver dependency.

Verified the types-only output compiles standalone under tsc --strict
with verbatimModuleSyntax, including enum unions and override imports.
Default output is unchanged.

Fixes #71.

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

Author: rtolsma

README.md

@@ -414,6 +414,23 @@ Note that overrides only change the generated *types* — converting values at
 runtime (for example, parsing a `numeric` string into a `Big`) is still up to
 your driver configuration.
 
+### Types-only generation
+
+Set `types_only: true` to generate only the `Args`/`Row` interfaces, enum
+union types, and override imports — no driver imports, query constants, or
+query functions. This is useful for sharing database types with a frontend
+that never runs the queries itself.
+
+```yaml
+codegen:
+- out: src/types/db
+  plugin: ts
+  options:
+    runtime: node
+    driver: pg
+    types_only: true
+```
+
 ## Development
 
 If you want to build and test sqlc-gen-typescript locally, follow these steps:

src/app.ts

@@ -51,6 +51,7 @@ interface Options {
   driver?: string;
   mysql2?: Mysql2Options
   overrides?: TypeOverride[];
+  types_only?: boolean;
 }
 
 interface Driver {
@@ -132,7 +133,9 @@ function codegen(input: GenerateRequest): GenerateResponse {
   }
 
   for (const [filename, queries] of querymap.entries()) {
-    const nodes = driver.preamble(queries);
+    // With types_only, emit only interfaces, enums, and override imports —
+    // no driver imports, query constants, or query functions
+    const nodes = options.types_only ? [] : driver.preamble(queries);
     // Insert custom type imports and enum declarations after the driver's
     // own imports, before any other declarations
     let insertAt = 0;
@@ -157,13 +160,15 @@ function codegen(input: GenerateRequest): GenerateResponse {
       const lowerName = query.name[0].toLowerCase() + query.name.slice(1);
       const textName = `${lowerName}Query`;
 
-      nodes.push(
-        queryDecl(
-          textName,
-          `-- name: ${query.name} ${query.cmd}
+      if (!options.types_only) {
+        nodes.push(
+          queryDecl(
+            textName,
+            `-- name: ${query.name} ${query.cmd}
 ${query.text}`
-        )
-      );
+          )
+        );
+      }
 
       let argIface = undefined;
       let returnIface = undefined;
@@ -176,7 +181,7 @@ ${query.text}`
         nodes.push(rowDecl(returnIface, driver, query.columns));
       }
 
-      switch (query.cmd) {
+      switch (options.types_only ? "" : query.cmd) {
         case ":exec": {
           nodes.push(
             driver.execDecl(lowerName, textName, argIface, query.params)