[docs] Update aspire do --list-steps docs to require step argument

src/frontend/src/content/docs/reference/cli/commands/aspire-do.mdx

@@ -96,15 +96,15 @@ The following options are available:
 
 Before executing a pipeline step, you can discover what steps are available in your application's pipeline and understand their dependencies. Aspire provides two complementary tools for this:
 
-- `aspire do --list-steps` — a quick, compact listing of every pipeline step with its direct dependencies and tags. Available on `aspire deploy`, `aspire publish`, `aspire destroy`, and `aspire do`. Useful for a fast "what would happen?" view before running a command.
+- `aspire do <step> --list-steps` — a quick, compact listing of every pipeline step with its direct dependencies and tags. Available on `aspire deploy`, `aspire publish`, `aspire destroy`, and `aspire do`. Useful for a fast "what would happen?" view before running a command. The `step` argument is required when using `--list-steps` with `aspire do`.
 - `aspire do diagnostics` — a verbose, in-depth report. The `diagnostics` step is itself part of the pipeline, so `aspire do diagnostics` runs it like any other step.
 
 ### Quick listing with `--list-steps`
 
-Running `aspire do --list-steps` produces a numbered list of every step in the pipeline, what each one depends on, and any tags it carries:
+Running `aspire do <step> --list-steps` produces a numbered list of every step in the pipeline, what each one depends on, and any tags it carries. The step argument is required — `aspire do` is always step-targeted, so `--list-steps` without a step has no meaningful scope. Omitting the step produces a friendly error that suggests concrete examples:
 
 ```bash title="Aspire CLI"
-aspire do --list-steps
+aspire do deploy --list-steps
 ```
 
 Example output:
@@ -162,13 +162,13 @@ Resources in your application can contribute their own custom steps, and you can
 
 The following examples demonstrate common pipeline operations:
 
-- Quickly list the steps in your pipeline:
+- Quickly list the steps in your pipeline for a specific step:
 
   ```bash title="Aspire CLI"
-  aspire do --list-steps
+  aspire do deploy --list-steps
   ```
 
-  This displays a compact view of every step with its dependencies and tags. Use it for a fast "what would happen?" check before running a pipeline command.
+  This displays a compact view of every step with its dependencies and tags. Use it for a fast "what would happen?" check before running a pipeline command. A step argument is required; `aspire do --list-steps` without a step produces a friendly error.
 
 - Run the `diagnostics` step for an in-depth report: