[adz624]

Summary

Support Rails 8 and Ruby 3.4.

• Widen gemspec / dependency constraints where needed
• Update CI / Appraisal gemfiles for Rails 8 and Ruby 3.4
• Keep existing Rails/Ruby matrices working

Test plan

• CI green on new matrix
• Spot-check in EIP or host app if relevant

Notes

• Do not publish gem to RubyGems from this PR
• Do not merge until reviewed

[sensui624]

已在此分支新增 .github/workflows/publish.yml（RubyGems Trusted Publishing，commit 235ce18）：master 上 gemspec 版本尚未發佈到 rubygems.org 時，先跑測試（Ruby 3.4.11 / gemfiles/rails_8.0.gemfile，bundle exec rake t），再以 OIDC 自動發佈。目前 gemspec 版本 1.0.0 已在 RubyGems 上，合併後會跳過發佈，直到版本號升級。

合併前需要先完成以下設定：

1. RubyGems Trusted Publisher：rubygems.org → warehouse_items → Trusted publishers，Repository superlanding/warehouse_items、Workflow publish.yml、Environment gem-publish。
2. GitHub environment gem-publish：Deployment branches 只允許 master。
3. master ruleset：套用到 default branch（禁止直接推送／force push、需透過 PR 合併）。