Fix logmetric array handling in tutorial and examples

[RomeoV]

Summary

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.

Changes

• Fixed docs/src/tutorial.md:98-101: Replaced single logmetric call with loop through array values
• Fixed examples/simple-with-mlflow.jl:47-50: Applied same correction

Problem

The tutorial and examples attempted to log entire arrays:

logmetric(mlf, exprun, "pricepath$(idx)", pricepath)  # ❌ pricepath is Array{Float64}

But logmetric only accepts single Float64 values:

logmetric(instance::MLFlow, run::Run, key::String, value::Float64; timestamp, step)

Solution

Updated to log each array element individually with step parameter:

# 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

Benefits

• ✅ Fixes the type error that prevented tutorial execution
• ✅ Maintains original intent of logging price paths over time
• ✅ Uses MLFlow's step parameter to track temporal sequence
• ✅ Creates proper time-series metrics that can be visualized in MLFlow UI
• ✅ Follows logmetric API requirements

Impact

• Makes the tutorial examples functional for metric logging
• Provides better MLFlow visualization of time-series data
• Demonstrates proper usage of MLFlow's step parameter for sequential data

Test plan

• Verified logmetric method signature requires Float64 values
• Confirmed step parameter usage for time-series data
• Both tutorial and example files updated consistently
• Solution maintains the intended data logging semantics

Fixes #63

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