opencode: add OAC

opencode/context/development/ai/mastra-ai/examples/workflow-example.md

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+<!-- Context: development/workflow-example | Priority: high | Version: 1.0 | Updated: 2026-02-15 -->
+
+# Example: Document Ingestion Workflow
+
+**Purpose**: Demonstrates a multi-step workflow with parallel processing.
+
+**Last Updated**: 2026-01-09
+
+---
+
+## Workflow Definition
+```typescript
+export const documentIngestionWorkflow = createWorkflow({
+  id: 'document-ingestion',
+  inputSchema: z.object({ filename: z.string(), fileBuffer: z.any() }),
+  outputSchema: z.object({ documentId: z.string(), success: z.boolean() }),
+})
+  .then(uploadStep)      // Step 1: Upload
+  .then(extractionStep)  // Step 2: Extract Text
+  .parallel([            // Step 3: Process in parallel
+    classificationStep,
+    summarizationStep
+  ])
+  .then(mergeResultsStep) // Step 4: Merge
+  .commit();
+```
+
+## Step Execution
+```typescript
+const uploadStep = createStep({
+  id: 'upload-document',
+  execute: async ({ inputData, mastra }) => {
+    const result = await documentUploadTool.execute(inputData, { mastra });
+    return result;
+  },
+});
+```
+
+**Reference**: `src/mastra/workflows/document-ingestion-with-classification-workflow.ts`
+**Related**:
+- concepts/workflows.md
+- concepts/agents-tools.md