For sure put in a sniffer. I have a hard-wired one in the kickspace beneath the stove. The alarm is in the forward cabin over my berth. You can also find any number of battery-powered models online or at big box stores or hardware stores.Very nice working galley!
I too have a shut-off panel for the tank solenoid. I'm keeping the shut off mostly for it's elbow configuration. We need the 90-degree turn at the bulkhead behind the stove to supply; straight down at the bulkhead - straight down at the stove, for the 2' hose between to function smoothly with the gimbaled stove.
In reality, that last flare fitting is in an enlarged hole in the rear bulkhead so it is easy to test.
I'm thinking I'll add a propane sniffer of some kind, and one at home which has a restaurant range with no thermocouples.
For better or worse, we have detectors for propane, carbon monoxide (diesel heater), and conventional smoke, with all the loud parts in the forward cabin, where we sleep.