Fix 1D convection and nonzero front values; check boundary conditions

- Fix the sign of the 1D convection (Robin) condition: the wall surface
  temperature now matches the analytical solution (7.6087 °C instead of
  10.294 °C in the 1D wall example). Update the regression test values.
- Impose front propagation Dirichlet values as Newton-Raphson increments,
  for both the matrix and frontal solvers, so nonzero constantValue
  boundaries converge. Add the u(0) = 1 case to the planar front test.
- Reuse the compute engine passed to solveAsync instead of ignoring it;
  without one, a temporary engine is created as before.
- Report unknown boundary condition types when solving, wrap plain-string
  conditions in an array with a warning, and report beam conditions that
  are not an array of conditions. Add boundaryConditions unit test.
- Use ["zeroGradient"] in the general form examples and tests.
- Replace the deprecated "constantTemp" in the README and examples, and
  link the documentation from the README.

Author: nikoscham

README.md

@@ -45,6 +45,8 @@ You can run simulations with FEAScript by calling its functions from JavaScript
 2. **[In JavaScript playgrounds](#use-feascript-in-javascript-playgrounds)** – Try FEAScript in interactive JavaScript playgrounds such as [CodePen](https://codepen.io/FEAScript) or [Scribbler](https://hub.scribbler.live/portfolio/#!nikoscham/FEAScript-Scribbler-examples).
 3. **[With Node.js](#use-feascript-with-nodejs)** – Use FEAScript in server-side JavaScript applications.
 
+📖 The **[FEAScript documentation](https://docs.feascript.com)** covers installation, the physical models and their equations, meshes, boundary conditions, solvers and the full API reference.
+
 #### Use FEAScript in the Browser
 
 You can use FEAScript in browser environments in three ways:
@@ -153,7 +155,7 @@ Here is a minimal browser-based example using the FEAScript API. Adapt paths, ph
 **Note:** The code above uses placeholder values that you should replace with appropriate options, e.g.:
 
 - "physicsModel" should be replaced with an actual solver type such as "heatConductionScript" for heat conduction problems
-- "conditionType" should be replaced with an actual boundary condition type such as "constantTemp"
+- "conditionType" should be replaced with an actual boundary condition type such as "constantTemperature"
 - "boundaryIndex" should be replaced with a string identifying the boundary
 
 Furthermore, the scripts under `examples/` contain Node.js examples. You can run them from the `FEAScript-core/` directory as follows:

dist/feascript-worker.esm.js

@@ -36,7 +36,7 @@ model.setMeshConfig({
 
 // Define boundary conditions
 model.addBoundaryCondition("0", ["constantValue", 1]); // Left boundary
-model.addBoundaryCondition("1", "zeroGradient"); // Right boundary
+model.addBoundaryCondition("1", ["zeroGradient"]); // Right boundary
 
 // Set solver method
 model.setSolverMethod("lusolve");