feat/PoC: settlement position reconstruction

[otto-link]

see: generate_network_alpha_model for road network, settlement connections
ref: https://www.researchgate.net/publication/257154745_Models_of_settlement_hierarchy_based_on_partial_evidence

Objective

Implement a PoC in HighMap to estimate plausible settlement positions from terrain data. The goal is to determine whether landscape constraints and optionnally known settlements can be combined into a settlement probability field from which missing settlements can be inferred.

Approach

Build a suitability/probability map from:

• terrain and slope;
• water availability / proximity;
• arable land;
• accessibility / transport routes;
• proximity to known settlements.

From the resulting field, extract candidate settlement positions using:

• local maxima;
• minimum-distance suppression;
• optionally stochastic sampling.

Each candidate should have a probability/suitability score.

Settlement hierarchy

As a second step, estimate a basic settlement importance from factors such as:

• local suitability;
• accessibility;
• catchment area;
• interaction with surrounding settlements.

A full Harris-Wilson / entropy-maximizing model is out of scope for the PoC.

The PoC should produce:

• a settlement probability heightmap;
• candidate settlement positions;
• a score/importance for each candidate.