okay so status update / solution:

by enabling the wifi component in the ESP-IDF, even though I didn't call any wifi-related code, it still allocated static memory buffers. if i comment out the wifi code, the linker helpfully optimizes out the entire wifi component and that memory isn't allocated!

now why would a few small memory buffers cause such a huge issue?

when it draws the framebuffer to the screen, the esp_lcd component helpfully queues a bunch of DMA transactions. max dma size is 32768, framebuffer is 230k bytes. but for some reason it can't DMA from the external memory, so for each dma transaction it allocates internal memory and copies the data there, and then... boom, out of memory. what a beyond fucking stupid oversight

i can't reprogram the esp_lcd component, soooo am i back to writing raw spi transactions 😭 its whatever but what the fuck yo