chore: bump engines.node to >=22.0.0 + explicit Node 22/24/26 CI matrix (#419)

Adopts the post-#7781 plugin policy: engines.node floats on >=22.0.0,
decoupled from core. Both Node 18 and Node 20 hit EOL in April 2026,
so the dropped install audience is zero.

The plugin's CI was pinned at a single Node major (most recently 25,
which is itself EOL). Replace with an explicit `[22, 24, 26]` matrix
on both backend-tests.yml and frontend-tests.yml so each supported
Node major is verified against an Etherpad core that actually allows
it:

- Node 22 against `v2.7.3` (last core release whose engines.node floor
  was 22.13.0). Verifies the plugin still works on the lowest declared
  floor.
- Node 24 against current `develop` (post-#7781 Node 24 floor).
- Node 26 against current `develop` (forward-compatibility check).

Local empirical verification: the plugin loaded, rendered all
comment templates / toolbar icons, and served `/p/<pad>` HTTP 200
with zero ERROR/FATAL log lines on both `(Node 22.22.3, Etherpad
v2.7.3)` and `(Node 24.14.0, Etherpad develop @ post-#7781)`.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: JohnMcLear

.github/workflows/backend-tests.yml

@@ -11,8 +11,23 @@ jobs:
     if: |
       (github.event_name != 'pull_request')
       || (github.event.pull_request.head.repo.id != github.event.pull_request.base.repo.id)
-    name: with Plugins
+    name: with Plugins (Node ${{ matrix.node }} / core ${{ matrix.core_ref || 'develop' }})
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      # Plugin floor is engines.node >=22 but current Etherpad core
+      # requires >=24 (engineStrict). Each cell pairs a Node version
+      # with a core ref that actually allows it: Node 22 against the
+      # last tag whose core floor was 22 (v2.7.3); Node 24 / 26 against
+      # current develop.
+      matrix:
+        include:
+          - node: '22'
+            core_ref: 'v2.7.3'
+          - node: '24'
+            core_ref: ''
+          - node: '26'
+            core_ref: ''
     steps:
       -
         name: Install libreoffice
@@ -25,11 +40,12 @@ jobs:
         uses: actions/checkout@v6
         with:
           repository: ether/etherpad-lite
+          ref: ${{ matrix.core_ref }}
           path: etherpad-lite
       - uses: actions/setup-node@v6
         name: Install Node.js
         with:
-          node-version: 25
+          node-version: ${{ matrix.node }}
       - uses: pnpm/action-setup@v6
         name: Install pnpm
         with:

.github/workflows/frontend-tests.yml

@@ -8,18 +8,35 @@ on:
 jobs:
   test-frontend:
     runs-on: ubuntu-latest
+    name: Playwright (Node ${{ matrix.node }} / core ${{ matrix.core_ref || 'develop' }})
+    strategy:
+      fail-fast: false
+      # Plugin floor is engines.node >=22 but current Etherpad core
+      # requires >=24 (engineStrict). Each cell pairs a Node version
+      # with a core ref that actually allows it: Node 22 against the
+      # last tag whose core floor was 22 (v2.7.3); Node 24 / 26 against
+      # current develop.
+      matrix:
+        include:
+          - node: '22'
+            core_ref: 'v2.7.3'
+          - node: '24'
+            core_ref: ''
+          - node: '26'
+            core_ref: ''
 
     steps:
       -
         name: Check out Etherpad core
         uses: actions/checkout@v6
         with:
           repository: ether/etherpad-lite
+          ref: ${{ matrix.core_ref }}
           path: etherpad-lite
       - uses: actions/setup-node@v6
         name: Install Node.js
         with:
-          node-version: 25
+          node-version: ${{ matrix.node }}
       - uses: pnpm/action-setup@v6
         name: Install pnpm
         with:

package.json

@@ -39,7 +39,7 @@
     "lint:fix": "eslint --fix ."
   },
   "engines": {
-    "node": ">=18.0.0"
+    "node": ">=22.0.0"
   },
   "repository": {
     "type": "git",