Add rod banks, xenon kinetics, and document feature set

AGENTS.md

@@ -2,6 +2,7 @@
 
 ## Project Structure & Module Organization
 All source code lives under `src/reactor_sim`. Submodules map to plant systems: `fuel.py` and `neutronics.py` govern fission power, `thermal.py` and `coolant.py` cover heat transfer and pumps, `turbine.py` drives the steam cycle, and `consumer.py` represents external electrical loads. High-level coordination happens in `reactor.py` and `simulation.py`. The convenience runner `run_simulation.py` executes the default scenario; add notebooks or scenario scripts under `experiments/` (create as needed). Keep assets such as plots or exported telemetry inside `artifacts/`.
+Feature catalog lives in `FEATURES.md`; update it whenever behavior is added or changed. Long-term realism tasks are tracked in `TODO.md`; keep it in sync as work progresses.
 
 ## Build, Test, and Development Commands
 - `.venv/bin/python -m reactor_sim.simulation` — run the default 10-minute transient and print JSON snapshots using the checked-in virtualenv.