Skip RBS rewrite when no markers are present

[mattkubej]

Summary

Avoid running Spoom's RBS-to-Sorbet-sig translator for typed Ruby files that cannot contain runtime-rewriteable RBS syntax.

Tapioca currently calls Spoom::Sorbet::Translate.rbs_comments_to_sorbet_sigs for every typed Ruby file loaded through the RBS rewriter. A large portion of typed files in Core do not contain RBS signatures or supported RBS annotations, so the translator often parses source only to return it unchanged.

This keeps the existing typed: gate and adds a conservative marker gate. Translation now runs only when source contains one of:

• #:
• #|
• # @abstract
• # @interface
• # @sealed
• # @final
• # @requires_ancestor:
• # @override
• # @overridable
• # @without_runtime

False positives are safe because they still use the existing translator. False negatives would be unsafe, so the annotation list is intentionally aligned with Spoom's currently supported runtime-rewrite annotations.

Core validation

Validated with a temporary Core CI experiment in shop/world#675510.

Clean timing run: https://buildkite.com/shopify/world-shopify-linters/builds/981200

Job	Time
marker guard	479.10s
stock Tapioca	590.41s

Delta: 111.31s faster (~18.9%).

The paired equivalence job on the same build produced byte-identical DSL RBI output:

Stock and marker-guard Tapioca DSL outputs are byte-identical.

Diagnostics from that run:

typed_files=60314
typed_marker_positive=22244
typed_marker_negative=38070
translate_calls=22244
rewrite_changed=21816
rewrite_unchanged=428
translate_errors=0