feat: add NANO.md memory system and Phase 2 foundations

Major additions:
- NANO.md hierarchical memory system (Claude Code CLAUDE.md compatible)
- Unified JSON-RPC client for MCP/LSP (saves ~250 LOC)
- Plugin system with YAML discovery (builtin/, ~/.nano/, .nano/)
- Undo/backup tool for file recovery
- SIGINT interrupt handler (Ctrl+C)
- Hooks actually integrated into CLI lifecycle
- JSON Schema specs for multi-language implementations
- 5 essential agents migrated to YAML

New commands:
- /memory - Show active memory files
- /remember - Save insights to NANO.md

Tests: 83/83 passing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: robotlearning123

NANO.md

@@ -0,0 +1,41 @@
+# nano-opencode Project Context
+
+## Project Overview
+nano-opencode is a minimal AI coding assistant (<5K LOC) with <50ms startup time.
+Future name: "jarvis" (inspired by Iron Man's AI assistant)
+
+## Architecture Decisions
+- TypeScript reference implementation (target: <3K LOC)
+- YAML-based plugin system for agents, skills, hooks
+- Unified JSON-RPC 2.0 client for MCP and LSP
+- Lazy loading everywhere for performance
+- SQLite for session persistence
+
+## Coding Standards
+- Use `bun` for package management and running
+- Tests: `npm test` (node:test built-in)
+- Prefer functional style over classes where possible
+- Keep files under 300 LOC
+- No emojis in code comments
+
+## Key Directories
+- `src/` - Core TypeScript implementation
+- `builtin/agents/` - Essential YAML agent definitions
+- `specs/interfaces/` - JSON Schema specifications
+- `test/` - Test files (*.test.ts)
+
+## Important Files
+- `src/cli.ts` - Main CLI REPL with interrupt handling
+- `src/agents/index.ts` - Agent system with memory injection
+- `src/memory/index.ts` - NANO.md memory system
+- `src/rpc/client.ts` - Unified JSON-RPC for MCP/LSP
+
+## Related Projects
+- jarvis: Future merge target at /home/robot/workspace/26-nano-opencode/jarvis
+
+## Current Phase
+Phase 2: Competitive Parity
+- [x] NANO.md memory system
+- [ ] Plan Mode (/plan command)
+- [ ] Ollama provider (local models)
+- [ ] Auto-commit git integration