fix: address Copilot review comments

- Set exit_code=0 in dry-run mode (CommandStep) instead of None, matching
  the COMPLETED status and not breaking expression evaluation
- Add dry_run parameter documentation to WorkflowEngine.execute() docstring
- Fix contradictory 'Run with --dry-run' hint messages in specify specify/plan
  commands (the message appeared inside the dry-run block itself)

Author: MiniMax-M2

src/specify_cli/__init__.py

@@ -616,7 +616,7 @@ def specify_specify(
         )
     console.print(f"\n[{status_color}]Status: {state.status.value}[/{status_color}]")
     if dry_run:
-        console.print("[dim]Run with --dry-run to see step details. Run without --dry-run to execute.[/dim]")
+        console.print("[dim]Run without --dry-run to execute.[/dim]")
 
 
 @specify_app.command("plan")
@@ -684,7 +684,7 @@ def specify_plan(
         )
     console.print(f"\n[{status_color}]Status: {state.status.value}[/{status_color}]")
     if dry_run:
-        console.print("[dim]Run with --dry-run to see step details. Run without --dry-run to execute.[/dim]")
+        console.print("[dim]Run without --dry-run to execute.[/dim]")
 
 
 # ===== Extension Commands =====

src/specify_cli/workflows/engine.py

@@ -427,6 +427,14 @@ def execute(
             User-provided input values.
         run_id:
             Optional run ID (auto-generated if not provided).
+        dry_run:
+            If ``True``, each step is executed normally but without
+            invoking the underlying AI integration (e.g. no CLI subprocess
+            is spawned for ``command`` steps, interactive gates return
+            ``COMPLETED`` immediately, etc.).  The workflow state is
+            still persisted to disk so ``specify workflow resume`` works.
+            Use this to preview the resolved inputs and prompts for a
+            workflow without making any AI API calls.
 
         Returns
         -------

src/specify_cli/workflows/steps/command/__init__.py

@@ -68,7 +68,7 @@ def execute(self, config: dict[str, Any], context: StepContext) -> StepResult:
             invoke_str = f"{command} {args_str}".strip()
             output["dispatched"] = False
             output["dry_run"] = True
-            output["exit_code"] = None
+            output["exit_code"] = 0
             output["stdout"] = ""
             output["stderr"] = ""
             output["invoke_command"] = invoke_str