Add release build script with Linux and Windows targets

Builds x86_64 Linux (native) and x86_64 Windows (MSVC via cargo-xwin).
Produces tar.gz for Linux, zip for Windows, plus SHA256 checksums.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1 +1,2 @@
 /target
+/release

release.sh

@@ -0,0 +1,151 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+VERSION=$(grep '^version' Cargo.toml | head -1 | sed 's/.*"\(.*\)"/\1/')
+RELEASE_DIR="release/v${VERSION}"
+BINARY_NAME="mouth"
+
+echo "=== Mouth Release Build v${VERSION} ==="
+echo ""
+
+# Ensure we're in the project root
+if [ ! -f Cargo.toml ]; then
+    echo "ERROR: Must be run from the project root (where Cargo.toml is)"
+    exit 1
+fi
+
+# Clean previous release artifacts for this version
+rm -rf "${RELEASE_DIR}"
+mkdir -p "${RELEASE_DIR}"
+
+# Track build results
+BUILT=()
+FAILED=()
+
+build_target() {
+    local target="$1"
+    local label="$2"
+    local ext="${3:-}"
+
+    echo "--- Building ${label} (${target}) ---"
+
+    if cargo build --release --target "${target}" 2>&1; then
+        local binary="target/${target}/release/${BINARY_NAME}${ext}"
+        if [ -f "${binary}" ]; then
+            local archive="${RELEASE_DIR}/${BINARY_NAME}-v${VERSION}-${target}"
+            if [ -n "${ext}" ]; then
+                # Windows: zip
+                local zip_name="${archive}.zip"
+                zip -j "${zip_name}" "${binary}" 2>/dev/null || {
+                    # Fallback if zip not installed
+                    cp "${binary}" "${archive}${ext}"
+                    echo "  -> ${archive}${ext}"
+                    BUILT+=("${archive}${ext}")
+                    return
+                }
+                echo "  -> ${zip_name}"
+                BUILT+=("${zip_name}")
+            else
+                # Linux/macOS: tar.gz
+                local tar_name="${archive}.tar.gz"
+                tar -czf "${tar_name}" -C "target/${target}/release" "${BINARY_NAME}"
+                echo "  -> ${tar_name}"
+                BUILT+=("${tar_name}")
+            fi
+        else
+            echo "  WARN: Binary not found at ${binary}"
+            FAILED+=("${label}")
+        fi
+    else
+        echo "  FAILED: ${label}"
+        FAILED+=("${label}")
+    fi
+    echo ""
+}
+
+# ============================================================
+# Build targets
+# ============================================================
+
+# Linux x86_64 (native — always available)
+build_target "x86_64-unknown-linux-gnu" "Linux x86_64"
+
+# Windows x86_64 (MSVC target via cargo-xwin)
+# ort requires the MSVC target — the GNU/MinGW target has no prebuilt
+# ONNX Runtime binaries. cargo-xwin cross-compiles using the MSVC
+# toolchain from Linux without needing a Windows machine.
+#
+# Install once:
+#   cargo install cargo-xwin
+#   rustup target add x86_64-pc-windows-msvc
+#
+if command -v cargo-xwin &>/dev/null && rustup target list --installed | grep -q x86_64-pc-windows-msvc; then
+    echo "--- Building Windows x86_64 (x86_64-pc-windows-msvc via cargo-xwin) ---"
+    if cargo xwin build --release --target x86_64-pc-windows-msvc 2>&1; then
+        local_binary="target/x86_64-pc-windows-msvc/release/${BINARY_NAME}.exe"
+        if [ -f "${local_binary}" ]; then
+            archive="${RELEASE_DIR}/${BINARY_NAME}-v${VERSION}-x86_64-pc-windows-msvc"
+            zip_name="${archive}.zip"
+            zip -j "${zip_name}" "${local_binary}" 2>/dev/null || {
+                cp "${local_binary}" "${archive}.exe"
+                echo "  -> ${archive}.exe"
+                BUILT+=("${archive}.exe")
+            }
+            if [ -f "${zip_name}" ]; then
+                echo "  -> ${zip_name}"
+                BUILT+=("${zip_name}")
+            fi
+        else
+            echo "  WARN: Binary not found"
+            FAILED+=("Windows x86_64 (MSVC)")
+        fi
+    else
+        echo "  FAILED: Windows x86_64 (MSVC)"
+        FAILED+=("Windows x86_64 (MSVC)")
+    fi
+    echo ""
+else
+    echo "--- Skipping Windows x86_64 ---"
+    echo "  cargo-xwin not installed or x86_64-pc-windows-msvc target missing."
+    echo "  To enable Windows builds from Linux:"
+    echo "    cargo install cargo-xwin"
+    echo "    rustup target add x86_64-pc-windows-msvc"
+    echo ""
+    FAILED+=("Windows x86_64 (not configured)")
+fi
+
+# ============================================================
+# Summary
+# ============================================================
+
+echo "=== Build Summary ==="
+echo ""
+
+if [ ${#BUILT[@]} -gt 0 ]; then
+    echo "Successful builds:"
+    for b in "${BUILT[@]}"; do
+        local_size=$(du -h "${b}" | cut -f1)
+        echo "  ${b} (${local_size})"
+    done
+fi
+
+if [ ${#FAILED[@]} -gt 0 ]; then
+    echo ""
+    echo "Failed / skipped builds:"
+    for f in "${FAILED[@]}"; do
+        echo "  ${f}"
+    done
+fi
+
+echo ""
+echo "Release artifacts in: ${RELEASE_DIR}/"
+echo ""
+
+# Generate checksums
+if [ ${#BUILT[@]} -gt 0 ]; then
+    echo "--- Checksums (SHA256) ---"
+    cd "${RELEASE_DIR}"
+    sha256sum * > checksums-sha256.txt 2>/dev/null || shasum -a 256 * > checksums-sha256.txt
+    cat checksums-sha256.txt
+    cd - > /dev/null
+fi