add el-install binary and SDK bundle to release pipeline

- lang/tools/install/el-install.el: El program that fetches the latest
  release from the Gitea API, downloads el-sdk-latest.tar.gz, and
  extracts it into ~/.el (or a custom prefix passed as argv[1])
- lang/tools/install/manifest.el: build manifest for the el-install package
- .gitea/workflows/sdk-release.yaml: build elb, epm, and el-install
  binaries; bundle elc + elb + epm + runtime files into el-sdk-latest.tar.gz;
  attach both the tarball and el-install binary to the Gitea release
  alongside the existing per-file GCP uploads

.gitea/workflows/sdk-release.yaml

@@ -59,6 +59,46 @@ jobs:
           echo "gen3 (self-hosted) elc built"
           dist/platform/elc --version || true
 
+      # Build elb binary
+      - name: Build elb
+        run: |
+          mkdir -p dist/bin
+          dist/platform/elc elb.el > dist/elb.c
+          gcc -O2 \
+            -I el-compiler/runtime \
+            dist/elb.c \
+            el-compiler/runtime/el_runtime.c \
+            -lcurl -lpthread \
+            -o dist/bin/elb
+          chmod +x dist/bin/elb
+          echo "elb built"
+
+      # Build epm binary (epm lives at repo root, not inside lang/)
+      - name: Build epm
+        run: |
+          dist/platform/elc ../epm/src/epm.el > dist/epm.c
+          gcc -O2 \
+            -I el-compiler/runtime \
+            dist/epm.c \
+            el-compiler/runtime/el_runtime.c \
+            -lcurl -lpthread \
+            -o dist/bin/epm
+          chmod +x dist/bin/epm
+          echo "epm built"
+
+      # Build el-install binary
+      - name: Build el-install
+        run: |
+          dist/platform/elc tools/install/el-install.el > dist/el-install.c
+          gcc -O2 \
+            -I el-compiler/runtime \
+            dist/el-install.c \
+            el-compiler/runtime/el_runtime.c \
+            -lcurl -lpthread \
+            -o dist/bin/el-install
+          chmod +x dist/bin/el-install
+          echo "el-install built"
+
       - name: Run tests — text
         run: |
           ELC="$(pwd)/dist/platform/elc" \
@@ -83,8 +123,24 @@ jobs:
           EL_HOME="$(pwd)" \
           bash tests/html_sanitizer/run.sh
 
-      # Publish / update the `latest` release with the three SDK assets
+      # Bundle the SDK tarball — runs from the repo root to reference lang/ paths correctly
+      - name: Bundle SDK tarball
+        working-directory: ${{ github.workspace }}
+        run: |
+          mkdir -p dist/sdk/bin dist/sdk/runtime
+          cp lang/dist/platform/elc          dist/sdk/bin/elc
+          cp lang/dist/bin/elb               dist/sdk/bin/elb
+          cp lang/dist/bin/epm               dist/sdk/bin/epm
+          cp lang/el-compiler/runtime/el_runtime.c  dist/sdk/runtime/
+          cp lang/el-compiler/runtime/el_runtime.h  dist/sdk/runtime/
+          cp lang/runtime/*.el               dist/sdk/runtime/
+          tar -czf dist/el-sdk-latest.tar.gz -C dist/sdk .
+          echo "SDK tarball bundled: dist/el-sdk-latest.tar.gz"
+          ls -lh dist/el-sdk-latest.tar.gz
+
+      # Publish / update the `latest` release with all SDK assets
       - name: Publish latest release
+        working-directory: ${{ github.workspace }}
         env:
           GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
           GITEA_API: https://git.neuralplatform.ai/api/v1
@@ -130,9 +186,14 @@ jobs:
               "${GITEA_API}/repos/${REPO}/releases/${RELEASE_ID}/assets"
           }
 
-          upload_asset dist/platform/elc                elc
-          upload_asset el-compiler/runtime/el_runtime.c el_runtime.c
-          upload_asset el-compiler/runtime/el_runtime.h el_runtime.h
+          # Per-file assets (downstream CI needs these individually)
+          upload_asset lang/dist/platform/elc                elc
+          upload_asset lang/el-compiler/runtime/el_runtime.c el_runtime.c
+          upload_asset lang/el-compiler/runtime/el_runtime.h el_runtime.h
+
+          # SDK bundle and installer binary
+          upload_asset dist/el-sdk-latest.tar.gz             el-sdk-latest.tar.gz
+          upload_asset lang/dist/bin/el-install              el-install
 
           echo "Release published successfully"