refactor: split compile.rs and simplify bytecode IR - #202

Summary

• Split query/compile.rs (1323 lines) into 7 focused modules:

  • mod.rs - compiler orchestration
  • capture.rs - capture effect emission
  • expressions.rs - node/field compilation
  • navigation.rs - anchor navigation modes
  • quantifier.rs - *, +, ? handling
  • scope.rs - struct/array scope management
  • sequences.rs - sequence and alternation compilation

• Simplify bytecode IR:

  • Remove unused ref_id from CallIR/ReturnIR
  • Add nav and node_field to CallIR for proper field constraint handling
  • Rename effect opcodes for clarity (A → Arr, S → Obj, E → Enum)

• Improve dump format with better column alignment

Test plan

• cargo test -p plotnik-lib passes (660 tests)
• CI passes