Refactor README and flake.nix for improved development environment setup; remove embedded Rust tooling references and add Cargo productivity tools

flake.nix

@@ -60,30 +60,22 @@
         {
           default = pkgs.mkShell {
             packages = with pkgs; [
+              # Rust toolchain (managed by fenix overlay)
               rustToolchain
+              rust-analyzer
+              # Build essentials
               git
               gnumake
               openssl
               pkg-config
+              # Cargo productivity tools
               cargo-deny
               cargo-edit
               cargo-watch
-              cargo-generate
-              rust-analyzer
-              rustup
-              # Embedded Rust tooling
-              probe-rs-tools
-              espflash
-              openocd
-              minicom
-              # RP2040 UF2 workflows
-              elf2uf2-rs
-              picotool
-              avrdude
-              pkgsCross.avr.buildPackages.libc
-              pkgsCross.avr.buildPackages.gcc
-              ravedude
+              # Code quality
               pre-commit
+              # Packaging
+              flatpak-builder
             ];
 
             env = {
@@ -98,20 +90,9 @@
                 echo "✓ Initialized git repository"
               fi
 
-              # Ensure user's Cargo-installed binaries are available
-              export PATH="$HOME/.cargo/bin:$PATH"
-
-              if command -v rustup >/dev/null 2>&1; then
-                echo "Ensuring common embedded Rust targets are available (idempotent)..."
-                rustup target add thumbv6m-none-eabi       >/dev/null 2>&1 || true  # Cortex-M0/M0+ (RP2040)
-                rustup target add thumbv7em-none-eabihf    >/dev/null 2>&1 || true  # Cortex-M4F/M7F (many STM32/nRF52)
-                rustup target add riscv32imc-unknown-none-elf >/dev/null 2>&1 || true
-                rustup target add riscv32imac-unknown-none-elf >/dev/null 2>&1 || true  # ESP32-C3 class
-                echo "Note: ESP32 Xtensa targets require espup/custom toolchains (see esp-rs)."
-              fi
-              echo "[FeDIY] Welcome to the Rust dev shell!"
-              echo "Tools: cargo, rustc, clippy, rustfmt, rust-analyzer, probe-rs, espflash, openocd, minicom, elf2uf2-rs, picotool, avrdude, ravedude"
-              echo "Run 'cargo build' to build, or 'nix run .#dev-helper' for a tool summary."
+              echo "[FeDIY] Welcome to the dev shell!"
+              echo "Tools: cargo, rustc, clippy, rustfmt, rust-analyzer, flatpak-builder"
+              echo "Run 'cargo build' to build, 'make flatpak-build' for Flatpak, or 'nix run .#dev-helper' for a tool summary."
               echo "See README.md for usage."
             '';
           };
@@ -130,10 +111,12 @@
           };
 
           devHelper = pkgs.writeShellScriptBin "dev-helper" ''
-            echo "Rust toolchain available:"
-            command -v cargo >/dev/null 2>&1 && cargo --version || true
-            command -v rustc >/dev/null 2>&1 && rustc --version || true
-            echo "This binary is built by Nix (packages.default)."
+            echo "=== FeDIY dev shell tools ==="
+            command -v cargo >/dev/null 2>&1 && echo "cargo: $(cargo --version)" || echo "cargo: not found"
+            command -v rustc >/dev/null 2>&1 && echo "rustc: $(rustc --version)" || echo "rustc: not found"
+            command -v rust-analyzer >/dev/null 2>&1 && echo "rust-analyzer: $(rust-analyzer --version)" || echo "rust-analyzer: not found"
+            command -v flatpak-builder >/dev/null 2>&1 && echo "flatpak-builder: $(flatpak-builder --version)" || echo "flatpak-builder: not found"
+            command -v pre-commit >/dev/null 2>&1 && echo "pre-commit: $(pre-commit --version)" || echo "pre-commit: not found"
           '';
         }
       );