Inline assembly: asm { ... } blocks

- Lexer: after \`asm\` keyword, next \`{\` triggers raw-text capture of
  the body until the matching \`}\`, emitted as a new \`AsmBody\` token
- Parser: \`asm { ... }\` produces \`Statement::InlineAsm(body, span)\`
- Analyzer: treats inline asm as opaque (no checks)
- IR: new \`IrOp::InlineAsm(String)\` variant that passes the body
  through the optimizer unchanged
- \`src/asm/inline_parser.rs\`: minimal 6502 mnemonic parser supporting
  every addressing mode we emit elsewhere (immediate, ZP/ABS with X/Y,
  indirect, indirect-X/Y, labels, branches, implied, accumulator)
- Both IR and AST codegen splice parsed instructions inline
- Integration test covers a mix of implied + immediate + ZP + A modes

https://claude.ai/code/session_01W6eQFStA66EuMKHUFo2rx3

tests/integration_test.rs

@@ -141,6 +141,27 @@ fn program_with_functions() {
     rom::validate_ines(&rom_data).expect("should be valid iNES");
 }
 
+#[test]
+fn program_with_inline_asm() {
+    let source = r#"
+        game "Asm" { mapper: NROM }
+        var x: u8 = 0
+        on frame {
+            asm {
+                LDA #$42
+                STA $10
+                INC $10
+                LSR A
+                CLC
+                ADC #$01
+            }
+        }
+        start Main
+    "#;
+    let rom_data = compile(source);
+    rom::validate_ines(&rom_data).expect("should be valid iNES");
+}
+
 #[test]
 fn program_with_while_loop() {
     let source = r#"