Update README.MD and add nano-claude-code v3.0 + original-source-code/src

- README.MD: add original-source-code and nano-claude-code sections, update
  overview table (4 subprojects), add v3.0 news entry, expand comparison table
  with memory/multi-agent/skills dimensions
- nano-claude-code v3.0: multi-agent package (multi_agent/), memory package
  (memory/), skill package (skill/) with built-in /commit and /review skills,
  context compression (compaction.py), tool registry plugin system, diff view,
  17 slash commands, 18 built-in tools, 101 tests (~5000 lines total)
- original-source-code/src: add raw TypeScript source tree (1884 files)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nano-claude-code/multi_agent/__init__.py

@@ -0,0 +1,23 @@
+"""Multi-agent package for nano-claude-code.
+
+Provides:
+  - AgentDefinition  — typed agent definition (name, system_prompt, model, tools)
+  - SubAgentTask     — lifecycle-tracked task
+  - SubAgentManager  — thread-pool manager for spawning agents
+  - load_agent_definitions / get_agent_definition — agent registry
+"""
+from .subagent import (
+    AgentDefinition,
+    SubAgentTask,
+    SubAgentManager,
+    load_agent_definitions,
+    get_agent_definition,
+)
+
+__all__ = [
+    "AgentDefinition",
+    "SubAgentTask",
+    "SubAgentManager",
+    "load_agent_definitions",
+    "get_agent_definition",
+]