fix: restore missing @types/node devDependency, bump to ^26

- @types/node was accidentally dropped from root package.json during the
  main rebase (packages/linting/* rely on typescript's shared "types":
  ["node"] tsconfig setting and broke CI: TS2688 cannot find type
  definition file for 'node')
- Bumped to ^26 via 'pnpm upgrade -r' to match node-setup's default
  Node 26 and align index-docs.yml/agent-context.yml, which were still
  pinned to Node 24

Author: odinr

.github/workflows/agent-context.yml

@@ -29,7 +29,7 @@ jobs:
 
       - uses: actions/setup-node@v7
         with:
-          node-version: 24
+          node-version: 26
 
       # Reads manifests directly — no dependency install needed.
       - name: Verify agent context

.github/workflows/index-docs.yml

@@ -50,7 +50,7 @@ jobs:
       - name: Setup Node.js
         uses: actions/setup-node@v7
         with:
-          node-version: 24
+          node-version: 26
 
       - name: Install dependencies
         run: pnpm install

package.json

@@ -72,6 +72,7 @@
     "@biomejs/biome": "2.5.8",
     "@changesets/changelog-github": "^1.0.0",
     "@changesets/cli": "^3.0.0",
+    "@types/node": "^26.2.0",
     "happy-dom": "^20.8.4",
     "tslib": "^2.6.1",
     "turbo": "^2.5.6",