pictures, but i figured it out. i guess technically i snapped a "before": basically what's happening is there are four different 14 gauge cables coming into the receptacle. from left to right:

• one runs to the outlet controlled by the left switch
• the next supplies power to the left switch (the "source")
• the next is the source for the right switch
• the last runs to the light fixture above the dining table

three of the four cables are 14/2, which means they have hot (black), neutral (white), and ground (bare) wires. the leftmost cable also has a secondary hot wire (red). this stumped me until i figured out that the outlet it supplies is "split", which means the bottom plug is always hot (supplied directly by the black source wire), but the upper plug is only hot when the switch is on (supplied by the red wire, which runs between a different set of terminals). like this (the image actually shows the red always hot, but they're interchangeable, i think): because i have no idea what i'm doing, i assumed at first that the red wire to the outlet and the red wires on the dimmers meant i needed three-way switches. after poking around a bit more, i realized single pole switches would suffice, but also that i needed a bunch of extra wire (the dimmers have weird integrated wiring and PCB internals). various trips to home depot later, i had all my bits.

i've done a fair bit of low voltage soldering and wiring, but mains current terrifies me. on the one hand, this means i'm vigilant about cutting the power before i get anywhere near a receptacle. the downside is i'm not super confident testing when the circuit is hot, so i have to rely on deduction. in this case, that meant wiring up the easy side (light fixture) first, capping off the rest, powering it up, then doing the opposite with the outlet, then putting it all together.

a funny thing schematics don't teach you is that one of the most difficult parts of wiring up a receptacle is physically fitting all the guts inside. 14 gauge solid core wire is both inflexible (you need pliers to make fine adjustments) and brittle (it'll snap if you bend it back and forth). in this case i had 9 wires inside the box just from the externals wires. wherever possible i left things as they were, but i had to add pigtails (short connections from the switches to the externals) for the hots and grounds. you also want to avoid leaving a rats nest, both for safety reasons and out of respect for the next person who has to open it up.

all this to say, i finally got it working. now the LED halogen replacement turns on and off as expected, the split wiring to the wall outlet works as before, and the weird touch-dimmers are safely tucked away in the basement on a growing pile of obsolete electronic debris.