chore: fix comments in evaluation_plans/typed_step.go

[eddie-knight]

Some things in this file were inaccurate or misplaced:

🤖

• The TypedStep doc described history, not the type. It said the payload assertion "used to live in a per-step VerifyPayload guard." That's a changelog fact belonging to a commit message, not a statement about what the type is or does today. It also wasn't wrong exactly, but it didn't pertain to the code as it now stands.
• AllSteps's doc claimed the catalog YAML does the filtering ("the catalog YAML naturally filters to the correct subset at evaluation time"). I checked the SDK source: filtering isn't something the YAML does. The suite looks up e.steps[assessment.Requirement.EntryId] for each requirement a catalog declares, so an assessment ID absent from that catalog is simply never looked up. The comment attributed the mechanism to the wrong component.
• The example in the inline placeholder referenced a CRA catalog (for id, steps := range CRA { ... }) that doesn't exist anywhere in this repo. It described a hypothetical rather than the actual code, so I removed the specific name and left it generic.

The rest of the trim (shortening the closure-naming rationale, pointing at pluginkit.FuncName instead of restating its doc) was tightening, not correcting inaccuracy.