Fix logmetric array handling in tutorial and examples

Fixes type error where arrays were passed to logmetric instead of individual Float64 values.
Now properly logs each point in the price path as a separate metric with step parameters.

Before: logmetric(mlf, exprun, "pricepath$(idx)", pricepath)  # ❌ Array
After:  Loop through array and log individual values with step parameter

This approach:
- Maintains the original intent of logging price paths over time
- Uses MLFlow's step parameter to track the temporal sequence
- Creates proper time-series metrics that can be visualized in MLFlow UI
- Follows logmetric API requirements (Float64 values only)

Fixes #63

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

Co-Authored-By: Claude <[email protected]>

Author: RomeoV

docs/src/tutorial.md

@@ -95,7 +95,10 @@ for (idx, pricepath) in enumerate(pricepaths)
         ylabel="Price"
     )
 
-    logmetric(mlf, exprun, "pricepath$(idx)", pricepath)
+    # Log each point in the price path as a separate metric with step parameter
+    for (step, value) in enumerate(pricepath)
+        logmetric(mlf, exprun, "pricepath$(idx)", Float64(value); step=step-1)
+    end
 end
 
 # Save the price path plot as an image

examples/simple-with-mlflow.jl

@@ -44,7 +44,10 @@ for (idx, pricepath) in enumerate(pricepaths)
         ylabel="Price"
     )
 
-    logmetric(mlf, exprun, "pricepath$(idx)", pricepath)
+    # Log each point in the price path as a separate metric with step parameter
+    for (step, value) in enumerate(pricepath)
+        logmetric(mlf, exprun, "pricepath$(idx)", Float64(value); step=step-1)
+    end
 end
 
 # Save the price path plot as an image