Address review feedback on no-self-package-imports rule

- `visitImports` now also reads `exportKind` so `export type { … } from`
  statements are classified as type-only, fixing a false positive in the
  self-import rule (and correctly skipping them in `no-undeclared-imports`
  too).
- The reachability-graph regex in `no-self-package-imports` skips
  `import type` / `export type` edges so files reachable only via
  type-only re-exports aren't pulled into a runtime bundle and no longer
  get false-positive same-entry errors.
- `SOURCE_EXTENSIONS` now includes `.mts` and `.cts` so entries and
  barrels using those extensions are followed correctly.
- The ESLint plugin changeset wording matches the `error` severity of
  the recommended config.
- Adds regression fixtures and RuleTester cases for `export type …` at
  both entries and for a file only reachable via a type-only edge.

Signed-off-by: Marat Dyatko <maratd@spotify.com>
Made-with: Cursor

packages/eslint-plugin/rules/no-self-package-imports.js

@@ -28,7 +28,16 @@ const getPackages = require('../lib/getPackages');
  * @property {string} sourceFile - The source file for the entry, relative to the package dir.
  */
 
-const SOURCE_EXTENSIONS = ['.ts', '.tsx', '.js', '.jsx', '.mjs', '.cjs'];
+const SOURCE_EXTENSIONS = [
+  '.ts',
+  '.tsx',
+  '.mts',
+  '.cts',
+  '.js',
+  '.jsx',
+  '.mjs',
+  '.cjs',
+];
 
 // Cache the per-package analysis across files lint invocations. The key is the
 // absolute package dir; the value is a Map from absolute file path to the set
@@ -84,9 +93,11 @@ function resolveSourcePath(fromFile, specifier) {
 }
 
 // Matches `from '...'` specifiers in `import`/`export ... from` statements.
-// Uses a non-greedy body so multi-line imports match cleanly.
+// Uses a non-greedy body so multi-line imports match cleanly. The negative
+// lookahead skips `import type` / `export type` statements because type-only
+// edges are erased at runtime and can't pull files into a runtime bundle.
 const FROM_SPEC_RE =
-  /(?:^|[\s;}])(?:import|export)\b[^"';]*?\bfrom\s*["']([^"']+)["']/gm;
+  /(?:^|[\s;}])(?:import|export)\b(?!\s+type\b)[^"';]*?\bfrom\s*["']([^"']+)["']/gm;
 // Matches side-effect imports: `import '...';`.
 const SIDE_EFFECT_IMPORT_RE = /(?:^|[\s;}])import\s*["']([^"']+)["']/gm;