<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Modernizes AI integration across the app.
> 
> - Upgrade `ai` to v6 and all `@ai-sdk/*` providers to v3/v4; add
`@ai-sdk/mcp`, remove `@openrouter/ai-sdk-provider`
> - Migrate from `LanguageModelV2` to `LanguageModel`/`LanguageModelV3`;
refactor fallback model to v3 streaming API
> - Switch OpenRouter to `createOpenAICompatible`
(`https://openrouter.ai/api/v1`)
> - Replace experimental MCP with `@ai-sdk/mcp` (`createMCPClient`);
update tool execution to `ToolExecutionOptions` and sanitize tool keys
> - Update AI message envelope to `ai@v6` and types
(`AiMessagesJsonV6`); adjust DB schema and parsing utilities
> - Update chat/local-agent handlers to v6 stream parts (reasoning/tool
parts), persist `aiMessagesJson`, and wire MCP tools into `ToolSet`
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
fc966595cbd9c6ff7d261497f00bfe79d0fff9e3. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Upgrade the app to AI SDK v6 to modernize model integrations, MCP
tooling, and streaming. This improves stability, unifies types on v3,
and removes the OpenRouter provider in favor of an OpenAI-compatible
setup.

- **Dependencies**
  - Upgraded ai to 6.0.14 and all @ai-sdk providers to v3/v4.
  - Added @ai-sdk/mcp; removed @openrouter/ai-sdk-provider.
  - Pinned @ai-sdk/provider to 3.0.2.
- Updated transitive deps (e.g., google-auth-library, gaxios) for Node
>=18.

- **Refactors**
- Moved from LanguageModelV2 to v3 and standardized on ai’s
LanguageModel.
  - Rebuilt fallback model to v3 spec with safer stream retries.
- Switched MCP client to createMCPClient and updated tool execution to
ToolExecutionOptions.
- Replaced OpenRouter integration with createOpenAICompatible (baseURL
https://openrouter.ai/api/v1).
- Updated AI messages envelope to "ai@v6"; older "ai@v5" envelopes are
ignored.

<sup>Written for commit fc966595cbd9c6ff7d261497f00bfe79d0fff9e3.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->