#89 fix(release): admit daisyui 2.x and fix the stale migration-registry spec

Summary

• docs-kit.gemspec: daisyui ">= 1.2", "< 2" → ">= 1.2", "< 3" so the daisyui 2.0 release can be adopted (docs/Gemfile.lock re-pinned to match).
• spec/generators/migration_registry_spec.rb: replace the 1.0-era "ships no migrations yet" assertion (made false by the 1.2.0 upgrade migration in #87) with checks that the 1.2.0 migration is registered and no registered migration targets a version above DocsKit::VERSION.
• CHANGELOG note.

That spec broke CI on main and the v1.2.0 Release run, so 1.2.0 never reached RubyGems. After merge: bin/release 1.2.1.

Test plan

• bundle exec rspec: 1007 examples, 0 failures, 92.6% line coverage (run against the sibling daisyui checkout, which already has 2.0's class merging)
• bundle exec rubocop clean
• CI green (3.3, 3.4, no-mcp gate)

https://claude.ai/code/session_01GtkdTTdUFkKiEU1dYH2JDS

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Summary by cubic

Allows adopting daisyui 2.x and fixes the stale migration-registry spec that failed CI and the 1.2.0 release run, so 1.2.0 never reached RubyGems.

• Loosens the daisyui dependency to >= 1.2, < 3 and re-pins docs/Gemfile.lock so sites can take daisyui 2.0.
• Replaces the 1.0-era "ships no migrations yet" assertion with checks that the 1.2.0 migration is registered and no registered migration targets a version above DocsKit::VERSION.