v0.2.0 - Deterministic simulation core

Introduces Tickline's deterministic C++23 reference simulation.

Included:

• explicit integer units
• fixed-step tick clock
• stable entity ordering
• authoritative world state
• scheduled velocity commands
• sequence and target-tick validation
• bounded integration
• fractional displacement preservation
• transactional world advancement
• canonical big-endian state encoding
• deterministic replay fingerprints
• boundary, replay, and sanitizer tests
• simulation contract documentation

The state fingerprint uses FNV-1a only for deterministic comparison. It is not used for evidence integrity or authentication.

Not included:

• networking
• protocol parsing
• collision or hit validation
• rollback or lag compensation
• multithreaded simulation
• cryptographic evidence hashing
• Unity visualization
• analytics