feat: add ARM64 (aarch64) architecture support for builds and packages

Add cross-architecture build support so the project can be developed on
ARM64 (Fedora aarch64 laptop) while still producing amd64 packages for
production. All build, package, publish, and install scripts are now
architecture-aware via shared arch-helper.sh detection.

- Add scripts/arch-helper.sh for shared architecture detection
- CI builds both amd64 and arm64 in matrix strategy
- nfpm.yaml uses NFPM_ARCH env var instead of hardcoded amd64
- Build scripts support MCPCTL_TARGET_ARCH for cross-compilation
- installlocal.sh auto-detects RPM/DEB and filters by architecture
- release.sh gains --both-arches flag for dual-arch releases
- Package cleanup is arch-scoped (won't clobber other arch's packages)
- build-mcpd.sh supports --platform and --multi-arch flags
- Add pnpm scripts: rpm:build:amd64, deb:build:arm64, release:both
- Conditional rpm/dpkg-deb checks for cross-distro compatibility

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

scripts/build-deb.sh

@@ -13,8 +13,14 @@ fi
 # Ensure tools are on PATH
 export PATH="$HOME/.npm-global/bin:$HOME/.bun/bin:$HOME/.local/bin:$PATH"
 
+# Architecture detection / cross-compilation support
+# MCPCTL_TARGET_ARCH overrides native detection (e.g. "amd64" or "arm64")
+source "$SCRIPT_DIR/arch-helper.sh"
+resolve_arch "${MCPCTL_TARGET_ARCH:-}"
+# Sets: NFPM_ARCH, BUN_TARGET, ARCH_SUFFIX
+
 # Check if binaries already exist (build-rpm.sh may have been run first)
-if [ ! -f dist/mcpctl ] || [ ! -f dist/mcpctl-local ]; then
+if [ ! -f "dist/mcpctl${ARCH_SUFFIX}" ] || [ ! -f "dist/mcpctl-local${ARCH_SUFFIX}" ]; then
   echo "==> Binaries not found, building from scratch..."
   echo ""
 
@@ -28,7 +34,7 @@ if [ ! -f dist/mcpctl ] || [ ! -f dist/mcpctl-local ]; then
   echo "==> Generating shell completions..."
   pnpm completions:generate
 
-  echo "==> Bundling standalone binaries..."
+  echo "==> Bundling standalone binaries (target: ${NFPM_ARCH})..."
   mkdir -p dist
 
   # Ink optionally imports react-devtools-core which isn't installed.
@@ -37,17 +43,28 @@ if [ ! -f dist/mcpctl ] || [ ! -f dist/mcpctl-local ]; then
     ln -s ../src/cli/stubs/react-devtools-core node_modules/react-devtools-core
   fi
 
-  bun build src/cli/src/index.ts --compile --outfile dist/mcpctl
-  bun build src/mcplocal/src/main.ts --compile --outfile dist/mcpctl-local
+  bun build src/cli/src/index.ts --compile ${BUN_TARGET:+--target "$BUN_TARGET"} --outfile "dist/mcpctl${ARCH_SUFFIX}"
+  bun build src/mcplocal/src/main.ts --compile ${BUN_TARGET:+--target "$BUN_TARGET"} --outfile "dist/mcpctl-local${ARCH_SUFFIX}"
 else
   echo "==> Using existing binaries in dist/"
 fi
 
-echo "==> Packaging DEB..."
-rm -f dist/mcpctl-*.deb dist/mcpctl_*.deb
+# If cross-compiling, copy arch-suffixed binaries to the names nfpm expects
+if [ -n "$ARCH_SUFFIX" ]; then
+  cp "dist/mcpctl${ARCH_SUFFIX}" dist/mcpctl
+  cp "dist/mcpctl-local${ARCH_SUFFIX}" dist/mcpctl-local
+fi
+
+echo "==> Packaging DEB (arch: ${NFPM_ARCH})..."
+# Only remove DEBs for the target arch (preserve cross-compiled packages)
+ls dist/mcpctl*_${NFPM_ARCH}.deb 2>/dev/null | xargs -r rm -f
+export NFPM_ARCH
 nfpm pkg --packager deb --target dist/
 
-DEB_FILE=$(ls dist/mcpctl*.deb 2>/dev/null | head -1)
+DEB_FILE=$(ls dist/mcpctl*.deb 2>/dev/null | grep -E "[._]${NFPM_ARCH}[._]" | head -1)
 echo "==> Built: $DEB_FILE"
 echo "    Size: $(du -h "$DEB_FILE" | cut -f1)"
-dpkg-deb --info "$DEB_FILE" 2>/dev/null || true
+# dpkg-deb may not be available on RPM-based systems (Fedora)
+if command -v dpkg-deb &>/dev/null; then
+  dpkg-deb --info "$DEB_FILE" 2>/dev/null || true
+fi