fix(linux): O_DIRECT fallback for dd on incompatible SD card readers

Some USB SD card readers don't support O_DIRECT, causing dd to fail
immediately with EINVAL. Now tries O_DIRECT first and falls back to
normal write if dd exits within 1 second.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "archr-flasher"
-version = "0.1.4"
+version = "0.1.5"
 description = "Arch R SD Card Flasher"
 authors = ["Arch R Linux"]
 edition = "2021"

src-tauri/src/flash.rs

@@ -261,9 +261,16 @@ for part in "${DEVICE}"*; do
         || true
 done
 
-# Write raw image with O_DIRECT (bypasses page cache, like RPi Imager)
-dd if="$IMAGE" of="$DEVICE" bs=4M oflag=direct conv=fsync status=none &
+# Write raw image — try O_DIRECT first (bypasses page cache, like RPi Imager),
+# fall back to normal write if device doesn't support it (EINVAL on some readers)
+dd if="$IMAGE" of="$DEVICE" bs=4M oflag=direct conv=fsync status=none 2>/dev/null &
 DD_PID=$!
+sleep 1
+if ! kill -0 $DD_PID 2>/dev/null; then
+    # dd with O_DIRECT exited immediately — retry without it
+    dd if="$IMAGE" of="$DEVICE" bs=4M conv=fsync status=none &
+    DD_PID=$!
+fi
 
 # Monitor dd progress via /proc/fdinfo
 while kill -0 $DD_PID 2>/dev/null; do

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://raw.githubusercontent.com/tauri-apps/tauri/dev/crates/tauri-config-schema/schema.json",
   "productName": "Arch R Flasher",
-  "version": "0.1.4",
+  "version": "0.1.5",
   "identifier": "com.archr.flasher",
   "build": {
     "frontendDist": "../src",