feat(stylelint-plugin): support stylelint v17 (#346)

* feat(stylelint-plugin): support stylelint v17

- Fix `utils.report()` index/endIndex to use node-relative offsets
  instead of absolute file offsets, as required by stylelint v17's
  stricter position argument handling (stylelint/stylelint#8217)
- Update devDependency to stylelint v17
- Add CI job to test with stylelint v16 for backward compatibility
- Add changeset

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: npm i

* ci: install stylelint@16 before setup-node-and-node-modules to avoid cache collision

`setup-node-and-node-modules` caches `node_modules` keyed by
`package-lock.json`. Installing stylelint@16 beforehand changes the
lock file so that the cache key differs from the stylelint@17 run,
preventing the wrong `node_modules` from being restored.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* ci: run only stylelint-plugin tests in CI stylelint job

The stylelint job was using `npx vitest --run --project unit` which ran
all unit tests filtered by path, instead of `npm run test` which correctly
runs only the specified package's tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* ci: remove vite/vitest cache from `test-stylelint-v16` job to avoid cache collision with `test` job

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: mizdra <pp.mizdra@gmail.com>

Author: 3 people

.changeset/support-stylelint-v17.md

@@ -0,0 +1,5 @@
+---
+'@css-modules-kit/stylelint-plugin': minor
+---
+
+feat(stylelint-plugin): support stylelint v17

.github/workflows/ci.yml

@@ -51,6 +51,18 @@ jobs:
           key: test-tools-${{ runner.arch }}-${{ runner.os }}-node-${{ matrix.node }}-${{ github.sha }}
           restore-keys: test-tools-${{ runner.arch }}-${{ runner.os }}-node-${{ matrix.node }}
       - run: npm run test
+  test-stylelint-v16:
+    runs-on: ubuntu-24.04-arm
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+      - run: npm i -D stylelint@16
+      - uses: ./.github/actions/setup-node-and-node-modules
+        with:
+          node-version: 22
+      - run: npm run test -- packages/stylelint-plugin
   vscode-test:
     strategy:
       fail-fast: false