fix: buffer stdout to handle chunked JSON and prevent test hanging

The listTools response (~25 KB) exceeds the macOS pipe buffer (16 KB),
causing it to arrive in multiple chunks. The previous test helper used
child.stdout.once('data') which only read the first chunk, resulting
in incomplete JSON and parse failures.

- Replace once('data') with a buffering reader that accumulates chunks
  until a complete newline-delimited JSON line is received
- Add killChild() helper that destroys stdin/stdout/stderr streams
  before sending SIGKILL to prevent the test process from hanging
- Wrap all test bodies in try/finally to ensure child cleanup on failure
- Increase sendRequest timeout from 10s to 30s for slow API responses
- Add Node.js version matrix (18, 20, 22) to CI workflow
- Update pnpm/action-setup from v3 to v4
- Trigger CI on all push/PR events, not just main branch

Author: titanism

.github/workflows/ci.yml

@@ -1,22 +1,30 @@
 name: CI
 on:
-  push:
-    branches:
-      - main
-  pull_request:
-    branches:
-      - main
+  - push
+  - pull_request
 jobs:
-  test:
-    runs-on: ubuntu-latest
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os:
+          - ubuntu-latest
+        node_version:
+          - 18
+          - 20
+          - 22
+    name: Node ${{ matrix.node_version }} on ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         with:
           version: 9
-      - uses: actions/setup-node@v4
+      - name: Setup node
+        uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version: ${{ matrix.node_version }}
           cache: 'pnpm'
-      - run: pnpm install
-      - run: pnpm test
+      - name: Install dependencies
+        run: pnpm install
+      - name: Run tests
+        run: pnpm test