chore: remove BMAD framework files and IDE configuration artifacts

Clean up unused BMAD workflow, agent, and command files across all IDE
configurations (.agent, .clinerules, .cursor, .gemini, .github, .kilocode,
.opencode) and internal module files (_bmad/bmb, _bmad/bmm).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

crates/solver/src/coupling.rs

@@ -22,13 +22,14 @@
 use entropyk_core::{CircuitId, Temperature, ThermalConductance};
 use petgraph::algo::{is_cyclic_directed, kosaraju_scc};
 use petgraph::graph::{DiGraph, NodeIndex};
+use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
 /// Thermal coupling between two circuits via a heat exchanger.
 ///
 /// Heat flows from `hot_circuit` to `cold_circuit` proportional to the
 /// temperature difference and thermal conductance (UA value).
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub struct ThermalCoupling {
     /// Circuit that supplies heat (higher temperature side).
     pub hot_circuit: CircuitId,