Summary

Add a stub .plot property on Result that raises a helpful ImportError if fluxopt-plot is not installed. This makes the accessor discoverable via tab-completion without coupling core to the plot package.

Design

# fluxopt/results.py
class Result:
    @property
    def plot(self):
        raise ImportError(
            "Plotting requires fluxopt-plot. "
            "Install it with: pip install fluxopt-plot"
        )

When fluxopt-plot is installed, it monkey-patches this property at import time:

# fluxopt_plot/__init__.py
from fluxopt.results import Result
from fluxopt_plot.accessor import PlotAccessor

Result.plot = property(lambda self: PlotAccessor(self))

Acceptance Criteria

• Result.plot raises ImportError with install instructions when fluxopt-plot is absent
• Property is discoverable in dir(result) and tab-completion
• Does not add any dependencies to core

Refs

Part of #47 — Architecture: Package Separation, SolutionResult Design, and Stability Tiers