Combat Commander Archivist
Move! Advance! Fire! Rout! Recover! Artillery Denied! Artillery Request! Command Confusion...say what?!
When completing the delivery of an artifact to the Depot, does your "X" character standee get placed on the Depot until you complete another delivery at a different location (as per the normal delivery process)?
No, it's not a "Delivery." It's the completion of a contract which has special rules. The rule is that you take an Bonus Action at the Depot to "deliver" the artifacts (all three of which must be dropped off at once).
Check the appendix for specific rules for the contracts.