ci: add nvim.wasm build and nightly release

Add a dedicated nvim.wasm build workflow and
include the resulting WASM artifact in nightly releases.

.github/workflows/build_wasm.yml

@@ -0,0 +1,62 @@
+name: nvim.wasm build
+
+on:
+  pull_request:
+    branches:
+      - 'master'
+      - 'release-[0-9]+.[0-9]+'
+    paths:
+      - 'build.zig'
+      - 'build.zig.zon'
+      - '.github/scripts/build_wasm.sh'
+      - '.github/workflows/build_wasm.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build-wasm:
+    name: Build nvim.wasm (Emscripten + Zig)
+    runs-on: ubuntu-24.04
+    timeout-minutes: 90
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - name: Set up Zig
+        uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
+        with:
+          version: 0.16.0
+          use-cache: false
+
+      - name: Cache emsdk, Binaryen & build outputs
+        uses: actions/cache@v6.1.0
+        with:
+          path: |
+            ./.emsdk
+            ./.binaryen
+          key: ${{ runner.os }}-wasm-${{ hashFiles('build.zig', 'build.zig.zon', '.github/scripts/build_wasm.sh') }}
+
+      - name: Install system deps
+        run: |
+          sudo apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive apt-get install -y \
+            python3 python3-pip curl unzip
+
+      - name: Install Emscripten SDK
+        run: |
+          set -euo pipefail
+          if [ ! -d ./.emsdk ]; then
+            git clone https://github.com/emscripten-core/emsdk.git ./.emsdk
+            cd ./.emsdk
+            ./emsdk install 6.0.2
+            ./emsdk activate 6.0.2
+            cd -
+          fi
+
+      - name: Build nvim.wasm
+        run: .github/scripts/build_wasm.sh

.github/workflows/release.yml

@@ -190,8 +190,49 @@ jobs:
             build/${{ matrix.archive_name }}.msi
           retention-days: 1
 
+  wasm:
+    needs: setup
+    runs-on: ubuntu-24.04
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - name: Set up Zig
+        uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
+        with:
+          version: 0.16.0
+          use-cache: false
+
+      - name: Install system deps
+        run: |
+          sudo apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive apt-get install -y \
+            python3 python3-pip curl unzip
+
+      - name: Install Emscripten SDK
+        run: |
+          set -euo pipefail
+          git clone https://github.com/emscripten-core/emsdk.git ./.emsdk
+          cd ./.emsdk
+          ./emsdk install 6.0.2
+          ./emsdk activate 6.0.2
+          cd -
+
+      - name: Build nvim.wasm
+        run: .github/scripts/build_wasm.sh
+        
+      - name: Upload wasm artifact
+        uses: actions/upload-artifact@v7
+        with:
+          name: nvim-wasm
+          path: build-wasm/*
+          retention-days: 1
+
   publish:
-    needs: [linux, macos, windows]
+    needs: [linux, macos, windows, wasm]
     runs-on: ubuntu-latest
     env:
       GH_REPO: ${{ github.repository }}
@@ -244,6 +285,6 @@ jobs:
         run: |
           envsubst < "$GITHUB_WORKSPACE/.github/workflows/notes.md" > "$RUNNER_TEMP/notes.md"
           if [ "$TAG_NAME" != "nightly" ]; then
-            gh release create stable $PRERELEASE --notes-file "$RUNNER_TEMP/notes.md" --title "$SUBJECT" --target $GITHUB_SHA nvim-macos-x86_64/* nvim-macos-arm64/* nvim-linux-x86_64/* nvim-linux-arm64/* nvim-appimage-x86_64/* nvim-appimage-arm64/* nvim-win-x86_64/* nvim-win-arm64/*
+            gh release create stable $PRERELEASE --notes-file "$RUNNER_TEMP/notes.md" --title "$SUBJECT" --target $GITHUB_SHA nvim-macos-x86_64/* nvim-macos-arm64/* nvim-linux-x86_64/* nvim-linux-arm64/* nvim-appimage-x86_64/* nvim-appimage-arm64/* nvim-win-x86_64/* nvim-win-arm64/* nvim-wasm/*
           fi
-          gh release create $TAG_NAME $PRERELEASE --notes-file "$RUNNER_TEMP/notes.md" --title "$SUBJECT" --target $GITHUB_SHA nvim-macos-x86_64/* nvim-macos-arm64/* nvim-linux-x86_64/* nvim-linux-arm64/* nvim-appimage-x86_64/* nvim-appimage-arm64/* nvim-win-x86_64/* nvim-win-arm64/*
+          gh release create $TAG_NAME $PRERELEASE --notes-file "$RUNNER_TEMP/notes.md" --title "$SUBJECT" --target $GITHUB_SHA nvim-macos-x86_64/* nvim-macos-arm64/* nvim-linux-x86_64/* nvim-linux-arm64/* nvim-appimage-x86_64/* nvim-appimage-arm64/* nvim-win-x86_64/* nvim-win-arm64/* nvim-wasm/*