Classes
class	ClusterIdentifier

class	Polarity

class	Population
Detailed Description

core/cluster_identifier.py — Abstract cluster state-space primitives (Layer 1).

Host-independent.  Implements the indexed cluster state space of
Ghoniem (2026), *A Generalized Graph-Based Cluster Dynamics Framework
for Irradiated Materials*, Section 2.1.

A cluster identifier is the four-tuple

    sigma = (chi, n, p, c)

  chi : polarity index in {-1, +1}  (-1 vacancy-type, +1 SIA-type)
  n   : size >= 1, the count of host Frenkel-pair sites of that polarity
        carried by the cluster
  p   : population label (a :class:`Population`)
  c   : composition vector, the counts of trapped non-host species
        (solutes / gases), e.g. (c_He, c_H)

The polarity index classifies a cluster by the sign of its net
Frenkel-pair content with respect to the host lattice.  It is unaffected
by solute trapping: a helium-vacancy cluster He_j V_n retains chi = -1
regardless of j.

Nothing here is host-specific.  A host material declares *which*
populations and *which* (chi, n, p, c) vertices are admissible; this
module only provides the vocabulary.
Classes

Detailed Description
