Does pickpocket’s ability create a chain that can be reacted to?

Yes. Pickpocket's "When you play me" ability is a Play Effect — a triggered ability — and triggered abilities go on the Chain as Pending Items, giving players a window to respond with Reactions (Rules 383.4.a, 401.1).

The trigger fires after Pickpocket resolves and enters the board (Rule 383.4.a.2). While it's on the Chain, an opponent can respond — e.g., by using an equip ability on the targeted gear to make it an illegal target on resolution, in which case the "if you do" clause means you don't get the Gold gear token (FAQ #6498). Note that Pickpocket itself is a permanent and enters play without a reaction window; only the ability after it is reactable.