Merge updates

.dockerignore

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+.github/
+.ruby-lsp/
+coverage/
+tmp/
+# Keep .git/ — needed for gemspec git ls-files and VCS checkout in tests
+.idea/
+.claude/
+.bundle/
+vendor/
+.specs/
+*.gem
+*.rbc
+*.log
+
+# Ignore report files
+*.attempt_*.png
+*.diff.png
+*.base.png
+*.attempt_*.webp
+*.diff.webp
+*.base.webp
+
+# OS files
+.DS_Store
+Thumbs.db

.gitattributes

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+*.gemspec diff=ruby
+*.rake    diff=ruby
+*.rb      diff=ruby
+*.md      diff=md

.github/actions/setup-ruby-and-dependencies/action.yml

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+---
+name: 'Setup Ruby and Cache'
+description: 'Set up Ruby environment and cache apt packages'
+inputs:
+  ruby-version:
+    description: 'Ruby version to set up'
+    required: true
+  ruby-cache-version:
+    description: 'Bundler cache version'
+    required: false
+  cache-apt-packages:
+    description: 'Whether to cache apt packages'
+    required: false
+    default: 'false'
+runs:
+  using: 'composite'
+  steps:
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ inputs.ruby-version }}
+        bundler-cache: true
+        cache-version: ${{ inputs.ruby-cache-version }}-v1
+
+    - name: Install and cache vips
+      if: ${{ inputs.cache-apt-packages == 'true' }}
+      uses: jetthoughts/cache-apt-pkgs-action@fix/upgrade-actions-cache-v5
+      with:
+        packages: libvips libglib2.0-0 libglib2.0-dev libwebp-dev libvips42 libpng-dev
+        version: tests-v2
+
+    - name: Install vips (fallback)
+      if: ${{ inputs.cache-apt-packages != 'true' }}
+      run: sudo apt-get -qq update && sudo apt-get -qq install -y libvips
+      shell: bash
+
+    - run: sudo sed -i 's/true/false/g' /etc/fonts/conf.d/10-yes-antialias.conf
+      shell: bash

.github/actions/upload-screenshots/action.yml

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+---
+name: 'Upload SnapDiff screenshots'
+description: 'Upload screenshot diffs, HTML report, and optionally comment on PR'
+inputs:
+  name:
+    description: 'Artifact name prefix'
+    required: true
+  report-path:
+    description: 'Path to the HTML report directory'
+    default: 'doc/screenshots'
+  retention-days:
+    description: 'Number of days to retain artifacts'
+    default: '2'
+  pr-comment:
+    description: 'Post PR comment with report link (requires pull-requests: write)'
+    default: 'false'
+outputs:
+  report-url:
+    description: 'Direct URL to the inline HTML report artifact'
+    value: ${{ steps.upload-report.outputs.artifact-url }}
+  report-full-url:
+    description: 'Direct URL to the full report artifact (with images)'
+    value: ${{ steps.upload-report-full.outputs.artifact-url }}
+runs:
+  using: 'composite'
+  steps:
+    - name: Upload screenshot diffs
+      uses: actions/upload-artifact@v7
+      with:
+        name: ${{ inputs.name }}-diffs
+        retention-days: ${{ inputs.retention-days }}
+        path: test/fixtures/app/doc/screenshots/
+        if-no-files-found: ignore
+
+    - name: Upload Capybara failure screenshots
+      uses: actions/upload-artifact@v7
+      with:
+        name: ${{ inputs.name }}-capybara-fails
+        retention-days: ${{ inputs.retention-days }}
+        path: tmp/capybara/screenshots-diffs/
+        if-no-files-found: ignore
+
+    - name: Check for HTML report
+      id: check-report
+      shell: bash
+      run: |
+        if [ -f "${{ inputs.report-path }}/snap_diff_report.html" ]; then
+          echo "exists=true" >> "$GITHUB_OUTPUT"
+        else
+          echo "exists=false" >> "$GITHUB_OUTPUT"
+        fi
+
+    - name: Prepare HTML report for inline preview
+      if: steps.check-report.outputs.exists == 'true'
+      shell: bash
+      run: cp "${{ inputs.report-path }}/snap_diff_report.html" "${{ inputs.report-path }}/${{ inputs.name }}-snap_diff-report.html"
+
+    - name: Upload HTML report (inline preview)
+      id: upload-report
+      if: steps.check-report.outputs.exists == 'true'
+      uses: actions/upload-artifact@v7
+      with:
+        name: ${{ inputs.name }}-snap_diff-report
+        retention-days: ${{ inputs.retention-days }}
+        path: ${{ inputs.report-path }}/${{ inputs.name }}-snap_diff-report.html
+        archive: false
+
+    - name: Upload HTML report with images (full download)
+      id: upload-report-full
+      if: steps.check-report.outputs.exists == 'true'
+      uses: actions/upload-artifact@v7
+      with:
+        name: ${{ inputs.name }}-report-full
+        retention-days: ${{ inputs.retention-days }}
+        path: ${{ inputs.report-path }}/
+
+    - name: Job summary
+      if: steps.check-report.outputs.exists == 'true'
+      shell: bash
+      run: |
+        cat >> "$GITHUB_STEP_SUMMARY" <<EOF
+        ### SnapDiff Report
+
+        | Artifact | Link |
+        |----------|------|
+        | HTML report (inline) | ${{ steps.upload-report.outputs.artifact-url || 'N/A' }} |
+        | Full report with images | ${{ steps.upload-report-full.outputs.artifact-url || 'N/A' }} |
+        EOF
+
+    - name: Find existing PR comment
+      if: inputs.pr-comment == 'true' && github.event_name == 'pull_request'
+      uses: peter-evans/find-comment@v3
+      id: find-comment
+      with:
+        issue-number: ${{ github.event.pull_request.number }}
+        comment-author: 'github-actions[bot]'
+        body-includes: 'Screenshot diffs'
+
+    - name: Comment PR with report link
+      if: inputs.pr-comment == 'true' && github.event_name == 'pull_request'
+      uses: peter-evans/create-or-update-comment@v5
+      with:
+        comment-id: ${{ steps.find-comment.outputs.comment-id }}
+        issue-number: ${{ github.event.pull_request.number }}
+        edit-mode: replace
+        body: |
+          ### Screenshot diffs detected
+
+          | Artifact | Link |
+          |----------|------|
+          | HTML report (inline) | ${{ steps.upload-report.outputs.artifact-url || 'N/A' }} |
+          | Full report with images | ${{ steps.upload-report-full.outputs.artifact-url || 'N/A' }} |
+          | [All artifacts](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}#artifacts) | Browse all |

.github/dependabot.yml

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+---
+version: 2
+
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/lint.yml

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+---
+name: Lint
+
+on:
+  pull_request:
+    branches: [ master ]
+    paths:
+      - '**.rb'
+      - '**.yml'
+      - '.github/workflows/lint.yml'
+      - '!bin/**'
+
+env:
+  RUBY_YJIT_ENABLE: 1
+
+jobs:
+  lint:
+    name: Ruby & YAML
+    runs-on: ubuntu-latest
+    timeout-minutes: 3
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '4.0'
+          bundler-cache: true
+
+      - name: Run Standard Ruby linter
+        run: bin/standardrb --no-fix --fail-fast
+
+      - name: Run Yaml linter
+        run: |
+          sudo apt-get install --fix-missing -qq --no-install-recommends yamllint
+          yamllint ./

.github/workflows/release.yml

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+---
+name: Release
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: "Release version (e.g., 1.12.0)"
+        required: true
+        type: string
+
+jobs:
+  release:
+    name: Release v${{ github.event.inputs.version }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    permissions:
+      id-token: write
+      contents: write
+
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ./.github/actions/setup-ruby-and-dependencies
+        with:
+          ruby-version: "4.0"
+          cache-apt-packages: true
+
+      - name: Verify version
+        run: |
+          GEM_VERSION="${{ github.event.inputs.version }}"
+          CODE_VERSION=$(ruby -I lib -r capybara/screenshot/diff/version -e "puts Capybara::Screenshot::Diff::VERSION")
+          if [ "$GEM_VERSION" != "$CODE_VERSION" ]; then
+            echo "Version mismatch: input=$GEM_VERSION code=$CODE_VERSION"
+            exit 1
+          fi
+
+      - name: Test
+        run: bundle exec rake test:unit
+
+      - name: Create tag
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git tag -a "v${{ github.event.inputs.version }}" -m "v${{ github.event.inputs.version }}"
+          git push origin "v${{ github.event.inputs.version }}"
+
+      - name: Publish to RubyGems
+        uses: rubygems/release-gem@v1
+
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v3
+        with:
+          tag_name: "v${{ github.event.inputs.version }}"
+          name: "v${{ github.event.inputs.version }}"
+          body: |
+            ## What's Changed
+
+            See [CHANGELOG.md](https://github.com/${{ github.repository }}/blob/main/CHANGELOG.md#v${{ github.event.inputs.version }}) for full details.
+
+            **Upgrade Guide:** [docs/UPGRADING.md](https://github.com/${{ github.repository }}/blob/main/docs/UPGRADING.md)
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}