fix: install script downloads prebuilt binaries from GitHub releases

Instead of compiling from source via cargo (slow), download the
prebuilt linux/darwin binaries from GitHub releases. Set USE_CARGO=1
to force building from source.

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

Author: thrashr888

install.sh

@@ -5,6 +5,10 @@
 # Run with: curl -fsSL https://raw.githubusercontent.com/thrashr888/agentkernel/main/install.sh | sh
 #
 # After installation, run: agentkernel setup
+#
+# Environment variables:
+#   INSTALL_DIR  - Where to install the binary (default: ~/.local/bin)
+#   USE_CARGO=1  - Force building from source via cargo instead of downloading
 
 set -euo pipefail
 
@@ -19,38 +23,82 @@ OS="$(uname -s | tr '[:upper:]' '[:lower:]')"
 ARCH="$(uname -m)"
 
 case "$ARCH" in
-    x86_64) ARCH="x86_64" ;;
-    aarch64|arm64) ARCH="aarch64" ;;
+    x86_64) ARCH_LABEL="x64" ;;
+    aarch64|arm64) ARCH_LABEL="arm64" ;;
     *)
         echo "Error: Unsupported architecture: $ARCH"
         exit 1
         ;;
 esac
 
-echo "Detected: $OS/$ARCH"
+echo "Detected: $OS/$ARCH_LABEL"
 
-# Check for Rust/Cargo (required for now since we don't have prebuilt binaries)
-if command -v cargo &>/dev/null; then
+# Force cargo build if requested
+if [ "${USE_CARGO:-}" = "1" ]; then
+    if ! command -v cargo &>/dev/null; then
+        echo "Error: USE_CARGO=1 but cargo not found."
+        exit 1
+    fi
     echo ""
-    echo "Installing via Cargo..."
-    cargo install --git "https://github.com/$REPO" agentkernel
-
+    echo "Installing via Cargo (forced)..."
+    cargo install --git "https://github.com/$REPO" agentkernel --force
     echo ""
     echo "=== Installation Complete ==="
-    echo ""
     echo "Next step: Run 'agentkernel setup' to download required components."
-    echo ""
     exit 0
 fi
 
-# No Cargo - try to download prebuilt binary (not available yet)
+# Download prebuilt binary from GitHub releases
+ASSET_NAME="agentkernel-${OS}-${ARCH_LABEL}.tar.gz"
+echo "Downloading prebuilt binary: $ASSET_NAME"
+
+# Get latest release download URL
+DOWNLOAD_URL="https://github.com/$REPO/releases/latest/download/$ASSET_NAME"
+
+# Create install directory
+mkdir -p "$INSTALL_DIR"
+
+# Download and extract
+TMPDIR="$(mktemp -d)"
+trap 'rm -rf "$TMPDIR"' EXIT
+
+if command -v curl &>/dev/null; then
+    curl -fsSL "$DOWNLOAD_URL" -o "$TMPDIR/$ASSET_NAME"
+elif command -v wget &>/dev/null; then
+    wget -q "$DOWNLOAD_URL" -O "$TMPDIR/$ASSET_NAME"
+else
+    echo "Error: Neither curl nor wget found."
+    exit 1
+fi
+
+tar xzf "$TMPDIR/$ASSET_NAME" -C "$TMPDIR"
+
+# Find the binary (may be in a subdirectory)
+BINARY="$(find "$TMPDIR" -name agentkernel -type f | head -1)"
+if [ -z "$BINARY" ]; then
+    echo "Error: agentkernel binary not found in archive."
+    exit 1
+fi
+
+chmod +x "$BINARY"
+mv "$BINARY" "$INSTALL_DIR/agentkernel"
+
 echo ""
-echo "Error: Rust/Cargo not found."
+echo "=== Installation Complete ==="
 echo ""
-echo "Install Rust first:"
-echo "  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh"
+echo "Installed to: $INSTALL_DIR/agentkernel"
+echo "Version: $("$INSTALL_DIR/agentkernel" --version 2>/dev/null || echo 'unknown')"
 echo ""
-echo "Then run this installer again, or install directly with:"
-echo "  cargo install --git https://github.com/$REPO agentkernel"
+
+# Check if install dir is in PATH
+case ":$PATH:" in
+    *":$INSTALL_DIR:"*) ;;
+    *)
+        echo "NOTE: $INSTALL_DIR is not in your PATH."
+        echo "Add it with: export PATH=\"$INSTALL_DIR:\$PATH\""
+        echo ""
+        ;;
+esac
+
+echo "Next step: Run 'agentkernel setup' to download required components."
 echo ""
-exit 1