Koru renames event keyword to tor

Renaming a fundamental keyword mid-development is a bold syntax move, but shedding the heavy baggage of "event" helps Koru clearly differentiate its execution paradigm.

• –Keyword syntax now directly maps to agentic handler declarations (e.g., `tor greet` defines a greetor).
• –Removes misleading connotations of heavy event loops and async overhead.
• –Leverages Sanskrit roots and agent-suffix naming to reframe low-level control flow.