Snapshot WIP: solver HP epic progress, BPHX/HX physics, BMAD skill refresh.

Capture uncommitted solver robustness work (regularization, domain errors, linear solver lifecycle, tube DP/MSH), web workbench updates, and synced BMAD skills across IDE agent folders before starting BPHX pressure-drop.

Co-authored-by: Cursor <cursoragent@cursor.com>

crates/solver/tests/convergence_criteria.rs

@@ -7,6 +7,7 @@
 
 use approx::assert_relative_eq;
 use entropyk_solver::{
+    system::{DEFAULT_MASS_FLOW_SEED_KG_S, MIN_SOLVER_PRESSURE_PA},
     CircuitConvergence, ConvergedState, ConvergenceCriteria, ConvergenceReport, ConvergenceStatus,
     FallbackSolver, NewtonConfig, PicardConfig, Solver, System,
 };
@@ -241,6 +242,7 @@ fn test_single_circuit_global_convergence() {
 use entropyk_components::port::ConnectedPort;
 use entropyk_components::{Component, ComponentError, JacobianBuilder, ResidualVector, StateSlice};
 
+/// CM1.3 self-loop mock: 3 equations constraining (ṁ, P, h) on a single edge.
 struct MockConvergingComponent;
 
 impl Component for MockConvergingComponent {
@@ -249,10 +251,12 @@ impl Component for MockConvergingComponent {
         state: &StateSlice,
         residuals: &mut ResidualVector,
     ) -> Result<(), ComponentError> {
-        // CM1.2: per-edge layout is (ṁ, P, h); index 0 is ṁ (pinned by the
-        // mass-flow closure), so this mock constrains P (index 1) and h (index 2).
-        residuals[0] = state[1] - 5.0;
-        residuals[1] = state[2] - 10.0;
+        // Pin P at the solver pressure floor (reachable under Newton clipping),
+        // h at a matching abstract target, and ṁ at the canonical seed so the
+        // single-edge self-loop is square (3 unknowns = 3 equations).
+        residuals[0] = state[1] - MIN_SOLVER_PRESSURE_PA;
+        residuals[1] = state[2] - MIN_SOLVER_PRESSURE_PA;
+        residuals[2] = state[0] - DEFAULT_MASS_FLOW_SEED_KG_S;
         Ok(())
     }
 
@@ -263,11 +267,12 @@ impl Component for MockConvergingComponent {
     ) -> Result<(), ComponentError> {
         jacobian.add_entry(0, 1, 1.0);
         jacobian.add_entry(1, 2, 1.0);
+        jacobian.add_entry(2, 0, 1.0);
         Ok(())
     }
 
     fn n_equations(&self) -> usize {
-        2
+        3
     }
     fn get_ports(&self) -> &[ConnectedPort] {
         &[]
@@ -278,8 +283,7 @@ impl Component for MockConvergingComponent {
 fn test_newton_with_criteria_single_circuit() {
     let mut sys = System::new();
     let node1 = sys.add_component(Box::new(MockConvergingComponent));
-    let node2 = sys.add_component(Box::new(MockConvergingComponent));
-    sys.add_edge(node1, node2).unwrap();
+    sys.add_edge(node1, node1).unwrap();
     sys.finalize().unwrap();
 
     let criteria = ConvergenceCriteria {