Stop teaching the old address flags in the docs

The flags are optional now and the page needs no addresses at all, so the examples no longer paste one build's numbers: screenshot.py is shown asking the firmware through tools/uvk5_buffers.py, and the webui example omits them entirely. The paragraph that said they default to one known build is replaced with what actually happens.

README.md

@@ -184,9 +184,11 @@ Five minutes from a checkout to a running radio on a web page.
     python3 tools/webui.py --qemu ~/src/qemu-7.2/build/qemu-system-arm \
         --elf assets/firmware/f4hwn.fieldops.v6.0.0.bin     # then open http://127.0.0.1:8080/
 
-`--frame-addr` and `--status-addr` default to one known build and move between builds;
-see [Web remote control](#web-remote-control) for how to find them. On Windows,
-`work/run-webui.ps1` wraps step 4 with this machine's paths.
+`--frame-addr` and `--status-addr` are optional, and normally omitted. The page draws the
+**display controller's own memory**, which is the screen for every firmware and needs no
+addresses at all; those two only serve the guest-RAM fallback, and `tools/uvk5_buffers.py`
+finds them in whatever firmware is running (`--frame-addr` on the command line skips the
+search). Nothing in this repository holds a build's addresses.
 
 Drop any `.bin` on the page to boot it. The page's **Firmware slots** table reads and
 writes the multi-system firmware's four slots in the flash image, and **Multiboot**