Fix generic ActiveJob signatures

[iamhaseebn]

Motivation

Generic ActiveJob subclasses currently generate bare job class references in perform_later signatures. Sorbet requires generic classes to include type arguments, so the generated RBI fails type checking.

Fixes #2233.

Implementation

• Detect generic ActiveJob subclasses using T::Generic === constant.
• Look up their non-fixed type members and use T.untyped for each generated type argument.
• Use the parameterized job type for both the callback parameter and the perform_later return type.
• Preserve existing signatures for non-generic jobs.

Tests

• Added regression coverage for jobs with one type member and multiple type members.
• Ran bundle exec bin/test spec/tapioca/dsl/compilers/active_job_spec.rb.
• Ran the complete suite: 821 tests, 3,190 assertions, 0 failures, 0 errors, 2 skips.
• Ran bundle exec bin/typecheck and bundle exec bin/style.
• Ran documentation, README, gem RBI, and shim verification checks.

[iamhaseebn]

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