docs: Only build reference docs if feature is enabled (#47273)

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Documentation**
* Reference documentation generation now only includes feature-enabled
SDK pages, so published docs better match what’s available.
* Legacy SDK reference pages are now shown selectively based on enabled
feature flags.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/docs/internals/generate-reference-markdown.ts

@@ -1,5 +1,6 @@
 import fs from 'node:fs/promises'
 import path from 'node:path'
+import { isFeatureEnabled, type Feature } from 'common/enabled-features'
 import matter from 'gray-matter'
 import yaml from 'js-yaml'
 import { fromMarkdown } from 'mdast-util-from-markdown'
@@ -41,6 +42,11 @@ type RefBase = {
   outFile: string
   /** Folder under docs/ref/ that holds .mdx sections for `type: "markdown"` entries. */
   mdxDir: string
+  /**
+   * Enabled-features flag gating this reference. When set and the feature is
+   * disabled in enabled-features.json, the file is not generated.
+   */
+  feature?: Feature
 }
 
 type SdkLegacyRef = RefBase & {
@@ -99,6 +105,7 @@ const REFERENCES: Ref[] = [
     mdxDir: path.join(MDX_ROOT, 'dart'),
     sectionsPath: path.join(GENERATED, 'dart.v2.sections.json'),
     functionsPath: path.join(GENERATED, 'dart.v2.functions.json'),
+    feature: 'sdk:dart',
   },
   {
     kind: 'sdk-legacy',
@@ -107,6 +114,7 @@ const REFERENCES: Ref[] = [
     mdxDir: path.join(MDX_ROOT, 'kotlin'),
     sectionsPath: path.join(GENERATED, 'kotlin.v1.sections.json'),
     functionsPath: path.join(GENERATED, 'kotlin.v1.functions.json'),
+    feature: 'sdk:kotlin',
   },
   {
     kind: 'sdk-legacy',
@@ -115,6 +123,7 @@ const REFERENCES: Ref[] = [
     mdxDir: path.join(MDX_ROOT, 'python'),
     sectionsPath: path.join(GENERATED, 'python.v2.sections.json'),
     functionsPath: path.join(GENERATED, 'python.v2.functions.json'),
+    feature: 'sdk:python',
   },
   {
     kind: 'sdk-legacy',
@@ -123,6 +132,7 @@ const REFERENCES: Ref[] = [
     mdxDir: path.join(MDX_ROOT, 'swift'),
     sectionsPath: path.join(GENERATED, 'swift.v2.sections.json'),
     functionsPath: path.join(GENERATED, 'swift.v2.functions.json'),
+    feature: 'sdk:swift',
   },
   {
     kind: 'sdk-legacy',
@@ -131,6 +141,7 @@ const REFERENCES: Ref[] = [
     mdxDir: path.join(MDX_ROOT, 'csharp'),
     sectionsPath: path.join(GENERATED, 'csharp.v0.sections.json'),
     functionsPath: path.join(GENERATED, 'csharp.v0.functions.json'),
+    feature: 'sdk:csharp',
   },
 ]
 
@@ -393,8 +404,10 @@ async function generate() {
     path.join(process.cwd(), 'content/reference/javascript/v2/typeSpec.json')
   )
 
+  const references = REFERENCES.filter((ref) => !ref.feature || isFeatureEnabled(ref.feature))
+
   await Promise.all(
-    REFERENCES.map(async (ref) => {
+    references.map(async (ref) => {
       let output: string
       switch (ref.kind) {
         case 'sdk-legacy':
@@ -424,7 +437,7 @@ async function generate() {
     })
   )
 
-  console.log(`Generated ${REFERENCES.length} markdown files under public/markdown/reference/`)
+  console.log(`Generated ${references.length} markdown files under public/markdown/reference/`)
 }
 
 generate()