Improve documentation for consciousness equation parameters

[Tristan-Stoltz-ERC]

Summary

The consciousness equation (IIT Φ computation) in symthaea-core/src/hdc/consciousness_equation.rs has many tunable parameters but limited documentation on their effects.

What needs documenting

Add rustdoc comments explaining:

• Each parameter's role in the Φ computation
• Valid ranges (many are 0.0–1.0 but some have different semantics)
• Impact on Φ scores — which parameters are most sensitive
• Substrate feasibility interaction — how substrate_feasibility modulates the final score
• Default values and why they were chosen

References

• Tononi, G. (2004). An information integration theory of consciousness. BMC Neuroscience.
• Our HAI paper in papers/latex/hai_paper.tex
• ConsciousnessEquationV2 is the current implementation
• ConsciousnessStateV2 holds the input parameters

Getting started

1. Read symthaea-core/src/hdc/consciousness_equation.rs
2. Look at how parameters are populated in src/cognitive_loop/consciousness_engine/
3. Add /// doc comments to each field in ConsciousnessStateV2
4. Verify docs build: cargo doc -p symthaea-core --no-deps