Add FirmMux updater app and docs updates

Author: nextcode4u

README.md

@@ -27,6 +27,7 @@ The script will:
 - Stage dependencies (RetroArch data, NTR Forwarder, CIAs)
 - Stage optional standalone pathfile package (mGBA/snes9x_3ds/DaedalusX64)
 - Show DSP firmware reminder (`sd:/3ds/dspfirm.cdc`)
+- On-device updater app is included at `sd:/3ds/firmmux-updater.3dsx` (FirmMux update only).
 
 Autoboot toggle (Settings):
 - OFF by default.
@@ -80,6 +81,11 @@ Run the PC setup script:
 - `python3 tools/firmmux_setup_pc.py`
 - Or: `python3 tools/firmmux_setup_pc.py --sd-root <SD_ROOT>`
 
+On-device updater note:
+
+- `sd:/3ds/firmmux-updater.3dsx` updates FirmMux files only.
+- Dependency staging remains PC-side via `tools/FirmMux_Setup.bat` or `tools/firmmux_setup_pc.py`.
+
 Health check also verifies:
 
 - `sd:/3ds/dspfirm.cdc` (if missing, dump DSP firmware from Rosalina menu)

SD/3ds/firmmux-updater.3dsx

@@ -22,9 +22,49 @@ build_cia_forwarder() {
     APP_AUTHOR='FirmMux Team' 2>&1 | tee -a "$log_file"
 }
 
+build_downloader() {
+  local dl_icon="assets/logodl.png"
+  if [ -f "$dl_icon" ]; then
+    local dims
+    dims="$(python3 - <<'PY'
+import struct
+try:
+    with open("assets/logodl.png", "rb") as f:
+        sig = f.read(8)
+        if sig != b"\x89PNG\r\n\x1a\n":
+            print("invalid")
+        else:
+            _len = f.read(4)
+            ctype = f.read(4)
+            if ctype != b'IHDR':
+                print("invalid")
+            else:
+                data = f.read(13)
+                w, h = struct.unpack(">II", data[:8])
+                print(f"{w}x{h}")
+except Exception:
+    print("invalid")
+PY
+)"
+    if [ "$dims" != "48x48" ]; then
+      echo "Downloader icon assets/logodl.png is $dims (expected 48x48). Falling back to assets/icon.png." | tee -a "$log_file"
+      dl_icon="assets/icon.png"
+    fi
+  else
+    dl_icon="assets/icon.png"
+  fi
+
+  make -B -j4 TARGET=firmmux_downloader \
+    APP_TITLE='FirmMux Updater' \
+    APP_DESCRIPTION='Update FirmMux on-device' \
+    APP_AUTHOR='FirmMux Team' \
+    APP_ICON="$dl_icon" 2>&1 | tee -a "$log_file"
+}
+
 stage_sd() {
   cp -f FirmMux.3dsx SD/3ds/FirmMux.3dsx
   cp -f FirmMux.smdh SD/3ds/FirmMux.smdh
+  mkdir -p SD/3ds
   mkdir -p SD/3ds/FirmMux
   mkdir -p SD/cias
   if [ -f boot.3dsx ]; then
@@ -33,6 +73,16 @@ stage_sd() {
   if [ -f boot.smdh ]; then
     cp -f boot.smdh SD/3ds/FirmMux/boot.smdh
   fi
+  if [ -f firmmux_downloader.3dsx ]; then
+    cp -f firmmux_downloader.3dsx SD/3ds/firmmux-updater.3dsx
+    rm -f SD/3ds/FirmMux/firmmux-downloader.3dsx
+    rm -f SD/3ds/firmmux-downloader.3dsx
+  fi
+  if [ -f firmmux_downloader.smdh ]; then
+    cp -f firmmux_downloader.smdh SD/3ds/firmmux-updater.smdh
+    rm -f SD/3ds/FirmMux/firmmux-downloader.smdh
+    rm -f SD/3ds/firmmux-downloader.smdh
+  fi
   echo "Staged SD binaries." | tee -a "$log_file"
 }
 
@@ -74,6 +124,14 @@ else
   exit 1
 fi
 
+echo "Building FirmMux downloader..."
+if build_downloader; then
+  echo "Downloader build succeeded. Log: $log_file"
+else
+  echo "Downloader build failed. Log: $log_file" >&2
+  exit 1
+fi
+
 echo "Building optional FirmMux CIA..."
 echo "Building FirmMux CIA forwarder ELF..."
 if build_cia_forwarder; then

SD/3ds/firmmux-updater.smdh

@@ -37,6 +37,9 @@ What it stages:
 - RetroArch 3DSX package files
 - Optional standalone pathfile package files (latest release)
 - Latest FirmMux release SD package (`FirmMux-SD.zip`) when using install/update modes
+- On-device updater app:
+  - `sd:/3ds/firmmux-updater.3dsx`
+  - `sd:/3ds/firmmux-updater.smdh`
 
 RetroArch staging note:
 
@@ -61,6 +64,11 @@ After script completes:
 - `L + D-Pad Down + Select` -> `Miscellaneous options` -> `Dump DSP firmware`
 4. Launch FirmMux and run Health check.
 
+On-device updater scope:
+
+- `firmmux-updater` updates FirmMux files only.
+- Use PC setup for dependency staging.
+
 CIA note:
 
 - `FirmMux.cia` is not the runtime app.

assets/logodl.png

@@ -9,6 +9,8 @@ sd:/
   3ds/
     FirmMux.3dsx
     FirmMux.smdh
+    firmmux-updater.3dsx
+    firmmux-updater.smdh
     FirmMux/
       boot.3dsx   # autoboot template used by Settings toggle
       boot.smdh   # autoboot name/icon metadata
@@ -65,6 +67,7 @@ sd:/
   - bannertool by carstene1ns: https://github.com/carstene1ns/3ds-bannertool
   - makerom from Project_CTR by 3DSGuy: https://github.com/3DSGuy/Project_CTR
 - Official runtime path is `sd:/3ds/FirmMux.3dsx` from default Homebrew Menu.
+- `sd:/3ds/firmmux-updater.3dsx` updates FirmMux files only (no dependency staging).
 - Standalone pathfile routing is optional.
 - To enable optional standalone routing, install marker + apps:
   - `sd:/3ds/emulators/pathfile`