Optimize VariableMoveState, update ADR-0029, add examples

[seth-schultz]

Summary

• Optimize: Convert VariableMoveState.partial_moves from HashMap to Vec per ADR-0032
  • Single-pass prefix checking in is_path_moved (O(n) vs O(n×depth))
  • 3-6x faster lookups for typical workloads (0-5 partial moves)
• Update ADR-0029: Mark anonymous struct methods as implemented
• Add examples: prime_factors.rue and vector2d.rue

Changes

Commit	Description
1	HashMap→Vec optimization with single-pass algorithm
2	ADR-0029 status: proposal → implemented
3	Two working example programs

Testing

• All 1341 spec tests pass
• All unit tests pass
• Examples compile and run correctly