MazeNET phase 2 step 1. Pulls inline IP/subnet allocation out of the
generator into decnet/topology/allocator.py so the editor + reconciler
can reuse the same primitives without duplicating logic.
- IPAllocator: stateful host-IP handout with reserve/release/is_free.
- SubnetAllocator: /24 handout under a base prefix, skips reservations.
- reserved_subnets(repo): collects claimed subnets across every
non-torn_down topology so concurrent drafts cannot collide.
- generate() accepts reserved_subnets= to skip existing claims.
Generator output is byte-identical under seed (behavior preserved).
Adds decnet/topology/ with:
- config.TopologyConfig: pydantic model driving generation (depth,
branching_factor, deckies_per_lan_min/max, bridge_forward_probability,
cross_edge_probability, subnet_base_prefix, service selection, seed).
Emits GeneratedTopology dataclass (lans, deckies, edges).
- status.TopologyStatus + assert_transition: seven-state machine with
an explicit legal-transition table. torn_down is terminal; degraded
is schema-reserved for future Healer use.
- generator.generate: deterministic DAG generation under config.seed.
Builds a tree of LANs (DMZ at root), plants deckies in each LAN,
promotes one decky per non-DMZ LAN to a parent bridge, and rolls
cross-edges per cross_edge_probability for DAG shape.
- persistence: persist() writes a plan to the repo as pending;
transition_status() enforces state-machine legality; hydrate() loads
topology + children into a single dict.
Covered by tests/topology/{test_status,test_generator,test_persistence}.
