It really is just a matter of time before some commander in Russia notices a huge mass of military hardware on the Polish side of the border and decides to push a button.

We’ve already seen shelling and rocket fire extend into the Russian mainland. This shit isn’t going to stay sandboxed forever. And then? I wouldn’t want to be Estonia right now.

… he may be tempted to risk a degree of escalation himself by, for example, interdicting western supplies before they arrive in Ukraine …

I wouldn’t be surprised to see this eventually. Iran has already (sort of) proven that retaliatory missile strikes on a NATO member doesn’t trigger Article 5. Russia would arguably be retaliating if only supply routes were targeted.