feat: Resumable Download Helper and Manifest Preservation

- Route downloads through local cache directory
- Automatically resume interrupted downloads from the byte offset
- `setup_uninstaller_context` checks if a fail had happened. If yes then
  CLI preserves existing manifest instead of wiping it.
- Interruption Signal Traps and Prompts

installers/install_agy.sh

@@ -96,7 +96,7 @@ install_agy() {
     fi
 
     log_info "Downloading release package..."
-        curl -fsSL "$url" -o "$staging_payload"
+    download_file "$url" "$staging_payload"
 
     # Verify SHA512 Checksum
     local actual_hash

installers/install_asciicinema.sh

@@ -76,7 +76,7 @@ install_asciicinema() {
     local download_url="https://github.com/asciinema/asciinema/releases/download/${latest_tag}/asciinema-${asciinema_arch}"
     
     log_info "Downloading asciinema ${latest_tag} for ${arch}..."
-    curl -fsSL "$download_url" -o "$TMP_DIR/asciinema"
+    download_file "$download_url" "$TMP_DIR/asciinema"
 
     log_info "Installing asciinema to /usr/local/bin..."
     sudo cp "$TMP_DIR/asciinema" /usr/local/bin/asciinema

installers/install_bat.sh

@@ -63,7 +63,7 @@ install_bat() {
 
         local deb_url="https://github.com/sharkdp/bat/releases/download/${latest_tag}/bat_${version}_${deb_arch}.deb"
         log_info "Downloading Bat from ${deb_url}..."
-            curl -fsSL "$deb_url" -o "$TMP_DIR/bat.deb"
+        download_file "$deb_url" "$TMP_DIR/bat.deb"
 
         log_info "Installing Bat package..."
         sudo apt install -y "$TMP_DIR/bat.deb"

installers/install_node.sh

@@ -45,8 +45,7 @@ install_nvm() {
 
     local nvm_url="https://github.com/nvm-sh/nvm/archive/refs/tags/${latest_tag}.tar.gz"
     log_info "Downloading NVM from $nvm_url..."
-
-        curl -fsSL "$nvm_url" -o "$TMP_DIR/nvm.tar.gz"
+    download_file "$nvm_url" "$TMP_DIR/nvm.tar.gz"
 
     log_info "Extracting NVM archive directly to $HOME/.nvm (stripping versioned subfolder to keep config generic)..."
     mkdir -p "$HOME/.nvm"

installers/install_nvim.sh

@@ -79,7 +79,7 @@ install_nvim() {
     local nvim_url="https://github.com/neovim/neovim/releases/download/v${NVIM_VERSION}/nvim-${nvim_arch}.tar.gz"
 
     log_info "Downloading Neovim v${NVIM_VERSION} for ${arch}..."
-        curl -fsSL "$nvim_url" -o "$TMP_DIR/nvim.tar.gz"
+    download_file "$nvim_url" "$TMP_DIR/nvim.tar.gz"
 
     tar -xzf "$TMP_DIR/nvim.tar.gz" -C "$TMP_DIR"
 

installers/install_pnpm.sh

@@ -34,7 +34,11 @@ trap cleanup EXIT
 # ─── Helper Functions ─────────────────────────────────────────────────
 
 download() {
+    if [ -n "${2:-}" ]; then
+        download_file "$1" "$2"
+    else
         curl -fsSL "$1"
+    fi
 }
 
 is_glibc_compatible() {
@@ -147,7 +151,7 @@ install_pnpm() {
 
     if [ "$major_version" -ge 11 ]; then
         # v11+: distributed as tarballs containing the binary and dist/ directory
-        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}.tar.gz" > "$TMP_DIR/pnpm.tar.gz" || {
+        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}.tar.gz" "$TMP_DIR/pnpm.tar.gz" || {
             log_error "Failed to download pnpm tarball."
             return 1
         }
@@ -162,7 +166,7 @@ install_pnpm() {
         }
     else
         # Older versions: distributed as a single executable binary
-        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}" > "$TMP_DIR/pnpm" || {
+        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}" "$TMP_DIR/pnpm" || {
             log_error "Failed to download pnpm binary."
             return 1
         }

installers/install_rust.sh

@@ -76,7 +76,7 @@ install_rust() {
     local dest="$TMP_DIR/rustup-init"
 
     log_info "Downloading rustup-init..."
-    curl -fsSL "$url" -o "$dest"
+    download_file "$url" "$dest"
 
     chmod +x "$dest"
 

installers/install_starship.sh

@@ -59,7 +59,7 @@ install_starship() {
 
     log_info "Downloading Starship from ${download_url}..."
     local archive="$TMP_DIR/starship.tar.gz"
-        curl -fsSL "$download_url" -o "$archive"
+    download_file "$download_url" "$archive"
 
     # Extract the binary
     log_info "Extracting Starship binary..."

installers/install_uv.sh

@@ -68,7 +68,7 @@ install_uv() {
 
     log_info "Downloading uv from ${download_url}..."
     local archive="$TMP_DIR/uv.tar.gz"
-        curl -fsSL "$download_url" -o "$archive"
+    download_file "$download_url" "$archive"
 
     # Extract the binaries
     log_info "Extracting uv binaries..."

installers/install_yazi.sh

@@ -76,7 +76,7 @@ install_yazi() {
 
         local deb_url="https://github.com/sxyazi/yazi/releases/download/${latest_tag}/yazi-x86_64-unknown-linux-gnu.deb"
         log_info "Downloading Yazi ${latest_tag} from ${deb_url}..."
-            curl -fsSL "$deb_url" -o "$TMP_DIR/yazi.deb"
+        download_file "$deb_url" "$TMP_DIR/yazi.deb"
 
         log_info "Installing Yazi package..."
         sudo apt install -y "$TMP_DIR/yazi.deb"