feat: Add OpenCode AI agent support

[newlandjia]

Summary

• Adds OpenCode (opencode.ai) configuration for AI-assisted development
• Provides project-specific context, patterns, and workflows for the monorepo

What's Included

Configuration (.opencode/opencode.jsonc)

• Schema-validated OpenCode configuration
• Context7 MCP integration for documentation lookup
• References to AGENTS.md for project guidelines

Guidelines (AGENTS.md)

• Project overview and architecture
• Quick start commands for CLI, Server, and App
• Code style conventions (TypeScript, indentation, naming)
• Component-specific guidelines for each part of the monorepo
• Testing patterns

Custom Commands (.opencode/command/)

Command	Description
/typecheck	Run TypeScript type checking per component
/test	Run tests per component
/i18n-check	Verify translations are complete
/rmslop	Remove AI-generated code slop

Skills (.opencode/skill/)

Skill	Description
expo-unistyles	Styling patterns with react-native-unistyles
i18n-translator	Translation function usage and patterns
prisma-server	Database operations and transaction patterns

Agents (.opencode/agent/)

Agent	Description
i18n-translator	Translates strings to all 9 supported languages

Why This Matters

OpenCode is an open-source AI coding agent that runs in the terminal. This configuration allows developers using OpenCode to:

1. Get project-specific context automatically loaded
2. Use custom commands for common workflows
3. Access skills that explain project-specific patterns
4. Have consistent AI assistance across the team

Testing

Verified the configuration structure matches OpenCode's expected format by comparing with the official opencode repository.

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This PR was created with assistance from an AI agent.