add binary type checker semantic pass

[cs01]

Summary

• New compile-time semantic pass rejects invalid binary operations (e.g., "hi" - 3, true + 8, [1,2] + "x")
• Catches mismatched types for arithmetic (-, *, /, %, etc.), addition (+), and comparison (<, >, etc.) operators
• Only checks literal/built-in types (no variable tracking yet) — catches the most obvious errors without self-hosting complexity
• Test fixtures are @test-skip since native compiler doesn't execute the pass yet

Test plan

• npm run verify:quick passes (tests + Stage 1 self-hosting)
• JS compiler correctly rejects true + 8, "hi" - 3, [1,2] + "x"
• Valid operations (1 + 2, "a" + "b", "count: " + 42) compile fine

🤖 Generated with Claude Code