chore(firmware): scaffold Spike 1 Blink crate

Generated from esp-rs/esp-idf-template for the ESP32-S3 std target.
src/main.rs toggles GPIO 2 every 500 ms and logs `blink N` over USB-
serial — the minimum bring-up surface called out in
docs/v0.1-mvp-technical.md (Spike 1: confirm toolchain, flash, and basic
GPIO). edition=2024 with rust-version=1.85.

No editor/render/git/usb/fs modules yet; those land per the spike
methodology when later spikes need them.

firmware/src/main.rs

@@ -0,0 +1,26 @@
+use esp_idf_svc::hal::delay::FreeRtos;
+use esp_idf_svc::hal::gpio::PinDriver;
+use esp_idf_svc::hal::peripherals::Peripherals;
+
+fn main() -> anyhow::Result<()> {
+    // Required once before any esp-idf-svc call; some runtime patches
+    // only link if this symbol is referenced. See esp-idf-template#71.
+    esp_idf_svc::sys::link_patches();
+    esp_idf_svc::log::EspLogger::initialize_default();
+
+    let peripherals = Peripherals::take()?;
+    let mut led = PinDriver::output(peripherals.pins.gpio2)?;
+
+    log::info!("Typoena Spike 1 — Blink on GPIO 2");
+
+    let mut n: u32 = 0;
+    loop {
+        led.set_high()?;
+        log::info!("blink {n}");
+        n = n.wrapping_add(1);
+        FreeRtos::delay_ms(500);
+
+        led.set_low()?;
+        FreeRtos::delay_ms(500);
+    }
+}