Add Colab-aware Pyomo bootstrap across notebooks

[Copilot]

Colab users hit missing pyomo when running the workshop notebooks.

• Colab bootstrap: Added a first-code-cell snippet to every notebook that installs Pyomo when running on Colab.
• Regression check: Added a test ensuring each notebook retains the Colab Pyomo install cell.

Example bootstrap cell:

import importlib.util, subprocess, sys

if "google.colab" in sys.modules and importlib.util.find_spec("pyomo") is None:
    subprocess.check_call([sys.executable, "-m", "pip", "install", "pyomo"])

Original prompt

Address #14

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[bernalde]

Some solvers will also be unavailable, also, make sure to run these notebooks in Colab and pre-load the results