Extends the @_init guard to def_method so that an ERB object created
via Marshal.load (which bypasses initialize) raises ArgumentError
instead of evaluating arbitrary source. def_module and def_class both
delegate to def_method and are covered by the same check.

Co-authored-by: Tristan Madani <TristanInSec@gmail.com>

	[ruby/timeout] Compatibility with Fiber scheduler.
	(https://github.com/ruby/timeout/pull/97)

	[Bug #21947]

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PR #15822 fixed the warning for direct hyphenated gem requires like
`benchmark/ips` → `benchmark-ips`. However, hyphenated gems often
provide multiple files under their namespace.

For example, `benchmark-ips` provides:
- benchmark/ips.rb
- benchmark/timing.rb
- benchmark/compare.rb

When requiring `benchmark/timing`, the previous fix only checked for
`benchmark-timing` gem (doesn't exist), not `benchmark-ips` which
actually provides the file.

This fix checks if ANY gem matching `{prefix}-*` is in the bundle
specs, which covers all subfeatures provided by hyphenated gems.

Reported in https://github.com/ruby/ruby/pull/15822#issuecomment-123456

https://github.com/ruby/syntax_suggest/commit/a81b92fcf2

[Bug #21847]