feat: migrate to svelte 5, modernise repo

eslint.config.ts

@@ -0,0 +1,80 @@
+import {defineConfig} from 'eslint/config'
+import {fileURLToPath} from 'node:url'
+import {includeIgnoreFile} from '@eslint/compat'
+import globals from 'globals'
+import js from '@eslint/js'
+import path from 'node:path'
+import prettier from 'eslint-config-prettier'
+import {createRequire} from 'node:module'
+
+import svelte from 'eslint-plugin-svelte'
+import tseslint from 'typescript-eslint'
+
+import type {Linter} from 'eslint'
+
+const studio = createRequire(import.meta.url)('@sanity/eslint-config-studio') as Linter.Config[]
+
+import appSvelteConfig from './sveltekit-app/svelte.config.js'
+
+const gitignorePath = fileURLToPath(new URL('./.gitignore', import.meta.url))
+const tsconfigRootDir = path.dirname(fileURLToPath(import.meta.url))
+
+export default defineConfig(
+  // Respect .gitignore
+  includeIgnoreFile(gitignorePath),
+  {
+    ignores: [
+      'eslint.config.ts',
+      'vite.config.ts',
+      'svelte.config.js',
+      '**/sanity.cli.ts',
+      '**/*.config.js',
+      '**/*.config.ts',
+    ],
+  },
+  // Base JS + TS
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+
+  // Svelte flat presets
+  ...svelte.configs['flat/recommended'],
+  ...svelte.configs['flat/prettier'],
+
+  // Global language options
+  {
+    languageOptions: {
+      globals: {...globals.browser, ...globals.node},
+      parserOptions: {
+        // Let typescript-eslint resolve per-package projects automatically
+        projectService: true,
+        // optional (safe if you keep it)
+        tsconfigRootDir,
+        extraFileExtensions: ['.svelte'],
+      },
+    },
+  },
+
+  // App config
+  {
+    files: ['sveltekit-app/**/*.svelte'],
+    languageOptions: {
+      parserOptions: {
+        parser: tseslint.parser,
+        svelteConfig: appSvelteConfig,
+      },
+    },
+  },
+  // Studio config
+  ...studio,
+
+  // Repo rules
+  {
+    rules: {
+      'no-console': 'error',
+      '@typescript-eslint/no-empty-object-type': 'off',
+    },
+  },
+
+  // Keep last
+  prettier,
+)