fix: composite pre/post conditions read the job status (#1242)

A composite action's child run context starts with empty step results, so a nested action's `post-if: success()` saw the composite's own result and still ran after the job had failed, which let `actions/cache` save caches from failed jobs.

The `job` context now always comes from the job's run context. Only `success()` and `failure()` in a composite's own main steps read the composite's result, matching GitHub Actions.

Assisted-by: Claude Code:claude-fable-5-1
Reviewed-on: https://gitea.com/gitea/runner/pulls/1242
Reviewed-by: bircni <[email protected]>
Co-authored-by: silverwind <[email protected]>

act/runner/step.go

@@ -299,7 +299,12 @@ func isStepEnabled(ctx context.Context, expr string, step step, stage stepStage)
 		defaultStatusCheck = exprparser.DefaultStatusCheckSuccess
 	}
 
-	runStep, err := EvalBool(ctx, rc.NewStepExpressionEvaluator(ctx, step), expr, defaultStatusCheck)
+	// success() and failure() in a composite's own main steps read the composite's result, other stages the job's
+	jobContext := rc.getJobContext()
+	if rc.Parent != nil && stage == stepStageMain && jobContext.Status != "cancelled" {
+		jobContext.Status = rc.ownStatus()
+	}
+	runStep, err := EvalBool(ctx, rc.newStepExpressionEvaluator(ctx, step, rc.actionInputs, jobContext), expr, defaultStatusCheck)
 	if err != nil {
 		return false, fmt.Errorf("if-expression %q evaluation failed: %s", expr, err)
 	}