[FEATURE]: add opencode support

[MaksimSkorobogatov]

Summary

Add OpenCode (terminal-based AI coding agent) to the list of supported agents in agentMemory.

Why

OpenCode is a popular open-source AI coding agent (Go-based TUI, ~140K GitHub stars) that already supports MCP servers natively via its opencode.json config. It would be a natural fit for agentMemory's persistent memory system.

MCP Server Config Format for OpenCode

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "agentmemory": {
      "type": "local",
      "command": ["node", "/path/to/mcp-server/server.js", "project-id", "/path/to/workspace"],
      "enabled": true
    }
  }
}

Note: OpenCode uses "type": "local" and "command" as an array (not "command" + "args" separately).

Proposed Changes

1. src/config.ts — Add OpenCode detection (check for opencode.json in workspace or opencode in PATH) and write MCP config to opencode.json instead of VS Code settings.

2. src/interceptor.ts — Add injectOpenCodeRules() method that:

   • Creates/updates AGENTS.md with agentMemory instructions at the project root
   • Creates .opencode/commands/memory-search.md custom command
   • Creates .opencode/commands/memory-write.md custom command

3. src/mcp-server/memory-bank-sync.ts — Add OpenCode agent config:

   {
     name: 'opencode',
     memoryBankPath: '.opencode/memory-bank',
     fileMapping: {
       'architecture.md': { type: 'architecture', tags: ['design', 'system'] },
       'patterns.md': { type: 'pattern', tags: ['patterns', 'design'] },
       'decisions.md': { type: 'decision', tags: ['decisions', 'tech'] },
       'features.md': { type: 'feature', tags: ['features', 'product'] }
     }
   }

   Also add sync to AGENTS.md since that's what OpenCode reads at session start.

4. Extension activation — OpenCode doesn't use VS Code extensions, so the integration would work via:

   • Manual MCP server configuration in opencode.json
   • Or a helper script that auto-configures opencode.json

OpenCode-Specific Notes

• OpenCode MCP tools are prefixed with the server name: agentmemory_memory_search, agentmemory_memory_write, etc.
• OpenCode supports both local (stdio) and remote (SSE) MCP servers
• OpenCode reads AGENTS.md at session start for project context — this is the equivalent of KiloCode's memory bank files
• Custom commands in .opencode/commands/ support $ARGUMENTS placeholder and frontmatter for description, agent, model

References

• OpenCode Docs
• OpenCode MCP Servers
• OpenCode Rules (AGENTS.md)
• OpenCode Commands
• OpenCode Agent Skills

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This issue is suitable as a task for a coding agent.

I can open a PR if it's welcome.