chore: install openagent opencode

Signed-off-by: Dmytro Stanchiev <git@dmytros.dev>

.opencode/context/development/ai/mastra-ai/errors/mastra-errors.md

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+<!-- Context: development/mastra-errors | Priority: medium | Version: 1.0 | Updated: 2026-02-15 -->
+
+# Errors: Mastra Implementation
+
+**Purpose**: Common errors, their causes, and recovery strategies.
+
+**Last Updated**: 2026-01-09
+
+---
+
+## Core Idea
+Errors in Mastra typically fall into three categories: AI generation failures, structured output validation errors, and context/resource missing errors.
+
+## Key Points
+- **AIGenerationError**: Occurs when the LLM fails to generate a response (e.g., safety filters, model downtime).
+- **StructuredOutputError**: Triggered when the LLM response doesn't match the Zod schema defined in the tool or step.
+- **RateLimitError**: Hit when exceeding provider limits. Includes a `retryAfter` value.
+- **MastraContextError**: Raised when a required resource (like `services` or `mastra` instance) is missing from the execution context.
+- **Retry Strategy**: Use `isRetryableError(error)` to determine if a transient failure can be recovered with exponential backoff.
+
+## Common Errors Table
+
+| Error | Cause | Fix |
+|-------|-------|-----|
+| `StructuredOutputError` | LLM hallucinated wrong JSON | Refine prompt or use simpler schema |
+| `RateLimitError` | Too many concurrent requests | Implement rate limiting or increase quota |
+| `NotFoundError` | Case or Document ID missing in DB | Check DB state before workflow start |
+| `MastraContextError` | `services` not passed to tool | Ensure `services` is in `ToolExecutionContext` |
+
+**Reference**: `src/lib/errors.ts`
+**Related**:
+- concepts/core.md
+- guides/testing.md