refactor(ruby-rails): version-agnostic skill with mandatory testing

[asharijuang]

Summary

• Remove hardcoded Ruby 3.1.3 / Rails 7.0 version locks — agent now detects versions from Gemfile.lock and .ruby-version
• Stop assuming specific gems (Avo, kredis, Jbuilder) are present — agent checks Gemfile first
• Add explicit testing requirements: every new feature, behavior change, or bug fix must include specs
• Add Run specs step to the "When Invoked" workflow and checklist

Files Changed (7 files, +94 -56)

File	What Changed
SKILL.md	Version detection step, generic gem references, testing enforcement in constraints/checklist
references/api-docs.md	Replaced hardcoded versions with "detect from Gemfile" guidance
references/api-development.md	Generic serialization references instead of Jbuilder-only
references/background-jobs.md	Support Sidekiq, GoodJob, Solid Queue, Active Job
references/openapi-documentation.md	Detect existing doc location instead of hardcoding path
references/rspec-testing.md	Added "New feature testing requirements" section with per-type guidance
scripts/helper.py	Updated checklist: version detection, generic gems, mandatory testing

Test plan

• Install the skill and invoke it on a Rails 7 project — verify it detects Rails 7 correctly
• Invoke on a Rails 8 project — verify no Rails 7-specific advice leaks through
• Ask it to add a new endpoint — verify it generates request specs automatically
• Ask it to fix a bug — verify it creates a regression spec