#359 workflow validate: false "Missing required inputs" when method args are set in the model definition

Description

swamp workflow validate reports Missing required inputs: <arg> for a model_method step whenever the required method argument is supplied by the model definition rather than the step's inputs: block. The check (#8, "Step inputs match required arguments") inspects only the step inputs: block and ignores methods.<method>.arguments already set in the model definition.

The workflow runs successfully — at runtime the definition's arguments are used — so the validation failure is a false positive. It also contradicts the docs: the data-chaining examples show command/shell workflow steps with no inputs: block at all.

Steps to reproduce

1. Create a command/shell model with methods.execute.arguments.run set.
2. Create a workflow with a model_method step calling that model's execute, with no inputs: block on the step.
3. Run swamp workflow validate <workflow> -> fails: Step inputs for '<step>' ... passed: false, "Missing required inputs: run".
4. Run swamp workflow run <workflow> -> succeeds, because the definition supplies run.

Expected

Validation should treat a required method argument as satisfied if the model definition already provides it; step inputs: are meant to override/supplement definition arguments, not be the sole source.

Environment

• swamp 20260515.175436.0-sha.2f8e98af
• macOS (darwin 25.3.0)