FIX: Resolve all paths to absolute before passing to NX

Root cause: Path.absolute() on Windows does NOT resolve '..' components.
sim_file_path was reaching NX as '...\studies\01_doe_landscape\..\..\models\Beam_sim1.sim'
NX likely can't resolve referenced parts from a path with '..' in it.

Fixes:
- nx_interface.py: glob from self.model_dir (resolved) not model_dir (raw)
- solver.py: sim_file.resolve() instead of sim_file.absolute()
- solve_simulation.py: os.path.abspath(sim_file_path) at entry point
- Diagnostic logging still in place for next run

projects/hydrotech-beam/studies/01_doe_landscape/_model_backup/README.md

@@ -0,0 +1,25 @@
+# Reference Models — Hydrotech Beam
+
+Golden copies of the NX model files. **Do not modify these directly.**
+
+Studies should copy these to their own `model/` folder and modify there.
+
+## Files
+
+| File | Description | Status |
+|------|-------------|--------|
+| `Beam.prt` | NX CAD part — sandwich I-beam with lightening holes | ⏳ Pending upload |
+| `Beam_fem1.fem` | FEM mesh file | ⏳ Pending upload |
+| `Beam_fem1_i.prt` | Idealized part for FEM | ⏳ Pending upload |
+| `Beam_sim1.sim` | Simulation file — SOL 101 static | ⏳ Pending upload |
+
+## Key Expression
+
+- `p173` — beam mass (kg)
+
+## Notes
+
+- ⏳ Awaiting Syncthing setup for project folder sync (dalidou ↔ server)
+- Model files will appear here once sync is live
+- Verify model rebuild across full design variable range before optimization
+- **Do NOT modify these reference copies** — studies copy them to their own `model/` folder

projects/hydrotech-beam/studies/01_doe_landscape/iterations/iter001/params.json

@@ -0,0 +1,15 @@
+{
+  "iteration": 1,
+  "expressions": {
+    "beam_half_core_thickness": 25.162,
+    "beam_face_thickness": 21.504,
+    "holes_diameter": 300.0,
+    "hole_count": 10.0
+  },
+  "trial_input": {
+    "beam_half_core_thickness": 25.162,
+    "beam_face_thickness": 21.504,
+    "holes_diameter": 300.0,
+    "hole_count": 10
+  }
+}

projects/hydrotech-beam/studies/01_doe_landscape/iterations/iter002/params.json

@@ -0,0 +1,15 @@
+{
+  "iteration": 2,
+  "expressions": {
+    "beam_half_core_thickness": 16.7813185433211,
+    "beam_face_thickness": 26.83364680743843,
+    "holes_diameter": 192.42062402658527,
+    "hole_count": 8.0
+  },
+  "trial_input": {
+    "beam_half_core_thickness": 16.7813185433211,
+    "beam_face_thickness": 26.83364680743843,
+    "holes_diameter": 192.42062402658527,
+    "hole_count": 8
+  }
+}

projects/hydrotech-beam/studies/01_doe_landscape/nx_interface.py

@@ -183,16 +183,18 @@ class AtomizerNXSolver:
             logger.info("Using existing model backup at %s", self._backup_dir)
 
         # Find the .sim file
-        sim_files = list(model_dir.glob("*.sim"))
+        # Use resolved model_dir for all path operations (NX needs clean absolute paths)
+        sim_files = list(self.model_dir.glob("*.sim"))
         if not sim_files:
-            raise FileNotFoundError(f"No .sim file found in {model_dir}")
-        self.sim_file = sim_files[0]
+            raise FileNotFoundError(f"No .sim file found in {self.model_dir}")
+        self.sim_file = sim_files[0]  # Already absolute (from resolved parent)
         logger.info("SIM file: %s", self.sim_file.name)
+        logger.info("SIM path: %s", self.sim_file)
 
         # Find the .prt file (for mass extraction)
-        prt_files = [f for f in model_dir.glob("*.prt") if "_i." not in f.name]
+        prt_files = [f for f in self.model_dir.glob("*.prt") if "_i." not in f.name]
         if not prt_files:
-            raise FileNotFoundError(f"No .prt file found in {model_dir}")
+            raise FileNotFoundError(f"No .prt file found in {self.model_dir}")
         self.prt_file = prt_files[0]
         logger.info("PRT file: %s", self.prt_file.name)