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>

.gitea/workflows/ci.yml

@@ -250,11 +250,14 @@ jobs:
         if: failure()
         run: cat /tmp/mcplocal.log || true
 
-  # ── Build & package RPM ───────────────────────────────────
+  # ── Build & package (both amd64 and arm64) ──────────────
 
   build:
     runs-on: ubuntu-latest
     needs: [lint, typecheck, test]
+    strategy:
+      matrix:
+        arch: [amd64, arm64]
     steps:
       - uses: actions/checkout@v4
 
@@ -283,11 +286,18 @@ jobs:
 
       - name: Install nfpm
         run: |
+          # nfpm itself runs on the CI runner (always x86_64); it cross-packages
+          # for the target arch via NFPM_ARCH env var — no ARM nfpm binary needed.
           curl -sL -o /tmp/nfpm.tar.gz "https://github.com/goreleaser/nfpm/releases/download/v2.45.0/nfpm_2.45.0_Linux_x86_64.tar.gz"
           tar xzf /tmp/nfpm.tar.gz -C /usr/local/bin nfpm
 
-      - name: Bundle standalone binaries
+      - name: Bundle standalone binaries (${{ matrix.arch }})
+        env:
+          MCPCTL_TARGET_ARCH: ${{ matrix.arch }}
         run: |
+          source scripts/arch-helper.sh
+          resolve_arch "$MCPCTL_TARGET_ARCH"
+
           mkdir -p dist
           # Stub for optional dep that Ink tries to import (only used when DEV=true)
           # Copy instead of symlink — bun can't read directory symlinks
@@ -295,26 +305,30 @@ jobs:
             rm -rf node_modules/react-devtools-core
             cp -r 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
+          bun build src/mcplocal/src/main.ts --compile ${BUN_TARGET:+--target "$BUN_TARGET"} --outfile dist/mcpctl-local
 
-      - name: Package RPM
+      - name: Package RPM (${{ matrix.arch }})
+        env:
+          NFPM_ARCH: ${{ matrix.arch }}
         run: nfpm pkg --packager rpm --target dist/
 
-      - name: Package DEB
+      - name: Package DEB (${{ matrix.arch }})
+        env:
+          NFPM_ARCH: ${{ matrix.arch }}
         run: nfpm pkg --packager deb --target dist/
 
       - name: Upload RPM artifact
         uses: actions/upload-artifact@v3
         with:
-          name: rpm-package
+          name: rpm-package-${{ matrix.arch }}
           path: dist/mcpctl-*.rpm
           retention-days: 7
 
       - name: Upload DEB artifact
         uses: actions/upload-artifact@v3
         with:
-          name: deb-package
+          name: deb-package-${{ matrix.arch }}
           path: dist/mcpctl*.deb
           retention-days: 7
 
@@ -328,19 +342,22 @@ jobs:
     runs-on: ubuntu-latest
     needs: [build]
     if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+    strategy:
+      matrix:
+        arch: [amd64, arm64]
     steps:
       - uses: actions/checkout@v4
 
       - name: Download RPM artifact
         uses: actions/download-artifact@v3
         with:
-          name: rpm-package
+          name: rpm-package-${{ matrix.arch }}
           path: dist/
 
       - name: Install rpm tools
         run: sudo apt-get update && sudo apt-get install -y rpm
 
-      - name: Publish RPM to Gitea
+      - name: Publish RPM (${{ matrix.arch }}) to Gitea
         env:
           GITEA_TOKEN: ${{ secrets.PACKAGES_TOKEN }}
           GITEA_URL: http://${{ env.GITEA_REGISTRY }}
@@ -379,16 +396,19 @@ jobs:
     runs-on: ubuntu-latest
     needs: [build]
     if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+    strategy:
+      matrix:
+        arch: [amd64, arm64]
     steps:
       - uses: actions/checkout@v4
 
       - name: Download DEB artifact
         uses: actions/download-artifact@v3
         with:
-          name: deb-package
+          name: deb-package-${{ matrix.arch }}
           path: dist/
 
-      - name: Publish DEB to Gitea
+      - name: Publish DEB (${{ matrix.arch }}) to Gitea
         env:
           GITEA_TOKEN: ${{ secrets.PACKAGES_TOKEN }}
           GITEA_URL: http://${{ env.GITEA_REGISTRY }}