Does Prismatic Bridge let you bypass a Companion's deck‑building restriction?

Look, I'm rolling a Commander deck with the companion "Zirda, the Dawn Mage" (your deck can't have cards with mana value 5 or more). I figured, why not slap a Prismatic Bridge on the battlefield, then let it reveal a 7‑cmc card from the top of my library? That card ends up on the battlefield without ever being in your opening deck.

Officially, the rule says the deck as it started the game must obey the companion's restriction. But Bridge literally takes a card from anywhere and puts it onto the board. Is that a loophole? Or is there some hidden clause that still counts the card as part of the deck for the purpose of the restriction? I've read a few rulings, but they're vague.

What do you think—are we cheating here, or is this legit? Looking for the precise rule citation if anyone's got it.

(Also, does this change if Bridge is animated by some effect that makes it a creature? Not that it matters, just curious.)