First of all, unless there are canon sources saying otherwise, the Shivans don't detect ships istantly so if there were destroyers trying to protect fleeing convoys, the Lucifer would have hardly detected them one second after it entered Sol.
No. But we know from the experience of Vasuda Prime that Shivans will make an attempt to attack any convoys trying to escape. At such short ranges, orbital rather than interplanetary, detection is easy. A destroyer would immediately draw the Lucifer down on any ships it's escorting and accomplish nothing positive. In fact, it would actually get anything it's guarding destroyed more rapidly.
With all the vital assets in the system, even if the Lucifer was invulnerable the GTA would have never left everything unguarded. Also:
That actually leads me to believe that, regardless of the odds, there were destroyers in Sol.
I'm not suggesting they're unguarded, though as I noted any destroyers (and possibly any cruisers) will simply ensure a more rapid destruction by drawing the Lucifer onto what they're guarding. Fightercraft are the only safe method of escort at this point, because they're not something the Lucifer is equipped to attack and will be ignored.
You're conveniently omitting the rest of the description, which says that Orions are only committed to active battle zones or areas that will become them: "where an Orion goes, war is sure to follow."
More importantly, don't forget that subspace tracking tech was extremely primitive, so thay may validate Droid's statement according to which a destroyer operating in Sol would have been unable to intercept the Lucifer into subspace if it entered the Gamma Draconis jump node.
The Bastion may have carried the only working prototype, but that's not strictly relevant. The Bastion itself never actually entered the subspace corridor. It's clear that the information can be transmitted to other ships and used by them.