docs: link reproducible ESP32-WROOM-32 real-silicon demo; update QEMU-only MCU caveat

README.md

@@ -65,9 +65,7 @@ quality bar. It is narrow, single-corpus (TinyStories), and sometimes incoherent
 
 ### What is NOT measured / NOT claimed
 - **Single seed only.** No multi-seed variance yet.
-- **MCU parity is QEMU only** (ARM Cortex-M3, MPS2-AN385), to FP32 epsilon. **No silicon
-  bring-up** is done in this repository. The RP2040 demo exceeds 264 KB SRAM at 944K — the
-  MCU claim is regime-dependent (it holds at the ~60K engine-default config, not at 944K).
+- **MCU parity is QEMU** (ARM Cortex-M3, MPS2-AN385) to FP32 epsilon, **plus a reproducible real-silicon demo**: the 944K checkpoint runs on a physical ESP32-WROOM-32, fully offline, ~1 tok/s — see [hardware/esp32-wroom32](https://github.com/TilelliLab/atome-lm/tree/main/hardware/esp32-wroom32) (prebuilt binary + serial log + one-command flash). That demo is a bare proof-of-execution, **not** a benchmark win and **not** productized bring-up; on a no-PSRAM ESP32 the 944K fits only with a short (seq=24) context window. The MCU claim stays **regime-dependent** (it holds at the ~60K engine-default config, not at 944K), and no same-chip head-to-head vs another MCU LM has been run.
 - **Router-entropy** is exposed for free as a per-token uncertainty signal, but its
   **calibration is unmeasured at this scale**.