feat: Multi-agent SDK — support OpenCode, Cursor, generic HTTP clients

[pitimon]

Inspiration

mem9 supports Claude Code, OpenCode, and OpenClaw from a single server with identical 5-tool interface. MemForge currently only has c-memforge for Claude Code.

Proposal

Create lightweight SDK adapters for other AI agents:

1. Generic HTTP client — curl/fetch-friendly REST API (already exists)
2. OpenCode plugin — TypeScript SDK with OpenCode hooks
3. Cursor adapter — mem_ingest already supports Cursor format, but no native plugin
4. Aider adapter — same as above

Scope

• Define minimal tool interface (store/search/get/update/delete) — 5 tools like mem9
• Reuse existing /api/ endpoints
• Agent-specific hooks for auto-capture

Value

Expand from Claude Code-only to multi-agent ecosystem. More agents = more observations = better knowledge graph.

Priority: HIGH