ci: skip Gemfile.lock BUNDLED WITH on ruby-head

Released bundlers (up to 4.0.11) reference Pathname::SEPARATOR_PAT,
which became a private constant on ruby-head, causing bundle install
to crash with NameError. The fix (ruby/rubygems#9529) is on master
but not yet released.

Use bundler's "version system" config to skip the lockfile-pinned
4.0.1 and use ruby-head's bundled bundler instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: soutaro

.github/workflows/ruby.yml

@@ -63,6 +63,9 @@ jobs:
         if: ${{ contains(matrix.ruby, 'head') }}
         run: |
           bundle config set force_ruby_platform true
+      - name: Ignore Gemfile.lock's BUNDLED WITH on ruby-head
+        if: ${{ contains(matrix.ruby, 'head') }}
+        run: bundle config set --local version system
       - name: Skip installing type checkers
         if: ${{ ! contains(matrix.job, 'typecheck_test') }}
         run: |
@@ -106,6 +109,9 @@ jobs:
         if: ${{ contains(matrix.ruby, 'head') }}
         run: |
           bundle config set force_ruby_platform true
+      - name: Ignore Gemfile.lock's BUNDLED WITH on ruby-head
+        if: ${{ contains(matrix.ruby, 'head') }}
+        run: bundle config set --local version system
       - name: bin/setup
         run: |
           bin/setup
@@ -140,6 +146,9 @@ jobs:
         if: ${{ contains(matrix.ruby, 'head') }}
         run: |
           bundle config set force_ruby_platform true
+      - name: Ignore Gemfile.lock's BUNDLED WITH on ruby-head
+        if: ${{ contains(matrix.ruby, 'head') }}
+        run: bundle config set --local version system
       - name: bin/setup
         run: |
           bin/setup

.github/workflows/windows.yml

@@ -35,6 +35,9 @@ jobs:
             bundled_gems = JSON.parse(res)["gems"].map{_1["gem"]}
             system "gem uninstall #{bundled_gems.join(" ")} --force", exception: true
           '
+      - name: Ignore Gemfile.lock's BUNDLED WITH on dev Ruby
+        if: ${{ matrix.ruby == 'ucrt' || matrix.ruby == 'mswin' }}
+        run: bundle config set --local version system
       - name: bundle install
         run: |
           bundle config set without profilers libs