64. A Smaller Node in Generated Parsers

• Change 63 in the generated Node runtime, whose Node is a type of the generated package: the kinds of a rule's nodes are set up in init with the rule table, those of struct types with structFields, and the emitted code makes CST nodes with the shared kinds of the reserved types. The typed converters read Type() and convert positions to the int spans of the typed values.
• Effect (min of 6 interleaved runs, Apple M3 Max): Parse JSON −2%/−3% (code points/bytes), CSV −8%/−12%, XML −7%/−5%, Arith_OperatorsRule −3%/−4%, Arith_LeftRec −2%/−4%, Minilang within noise, Outline and Recovery +1% to +5% (noise-level); allocation −10% to −21% (JSON 12.8 → 10.7 MB, Outline 12.8 → 10.2 MB); ParseAST and Recognize unchanged within noise.