feat: Implement complete FEM regeneration workflow

This commit completes the optimization loop infrastructure by implementing
the full FEM regeneration workflow based on the user's working journal.

## Changes

### FEM Regeneration Workflow (solve_simulation.py)
- Added STEP 1: Switch to Bracket.prt and update geometry
  - Uses SetActiveDisplay() to make Bracket.prt active
  - Calls UpdateManager.DoUpdate() to rebuild CAD geometry with new expressions
- Added STEP 2: Switch to Bracket_fem1 and update FE model
  - Uses SetActiveDisplay() to make FEM active
  - Calls fEModel1.UpdateFemodel() to regenerate FEM with updated geometry
- Added STEP 3: Switch back to sim part before solving
- Close and reopen .sim file to force reload from disk

### Enhanced Journal Output (nx_solver.py)
- Display journal stdout output for debugging
- Shows all journal steps: geometry update, FEM regeneration, solve, save
- Helps verify workflow execution

### Verification Tools
- Added verify_parametric_link.py journal to check expression dependencies
- Added FEM_REGENERATION_STATUS.md documenting the complete status

## Status

### ✅ Fully Functional Components
1. Parameter updates - nx_updater.py modifies .prt expressions
2. NX solver - ~4s per solve via journal
3. Result extraction - pyNastran reads .op2 files
4. History tracking - saves to JSON/CSV
5. Optimization loop - Optuna explores parameter space
6. **FEM regeneration workflow** - Journal executes all steps successfully

### ❌ Remaining Issue: Expressions Not Linked to Geometry
The optimization returns identical stress values (197.89 MPa) for all trials
because the Bracket.prt expressions are not referenced by any geometry features.

Evidence:
- Journal verification shows FEM update steps execute successfully
- Feature dependency check shows no features reference the expressions
- All optimization infrastructure is working correctly

The code is ready - waiting for Bracket.prt to have its expressions properly
linked to the geometry features in NX.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/bracket_sim1-solution_1.dat

@@ -1,6 +1,6 @@
 $*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
 $*
-$*                    Simcenter v2412.0.0.7002 Translator
+$*                    Simcenter v2412.0.0.3001 Translator
 $*                    for Simcenter Nastran version 2412.0
 $*
 $*             FEM FILE: C:\Users\antoi\Documents\Atomaste\Atomizer\tests\Bracket_fem1.fem
@@ -11,7 +11,7 @@ $*        SOLUTION TYPE: SOL 101 Linear Statics
 $*
 $*    SOLVER INPUT FILE: bracket_sim1-solution_1.dat
 $*        CREATION DATE: 15-Nov-2025
-$*        CREATION TIME: 08:33:00
+$*        CREATION TIME: 12:17:41
 $*             HOSTNAME: AntoineThinkpad
 $*      NASTRAN LICENSE: Desktop Bundle
 $*