ci: pin Node 24 and setup-node@v7

Node 20 is deprecated on GitHub Actions runners. Use setup-node@v7
(node24 action runtime) and install Node 24 for webjs tests so all CI
jobs avoid the deprecation warning.

.github/workflows/ci.yml

@@ -20,9 +20,10 @@ jobs:
       - uses: actions/setup-go@v7
         with:
           go-version-file: go.mod
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
-          node-version: "20"
+          # Node 20 is EOL on GHA runners; pin current Actions default (24).
+          node-version: "24"
       - name: gofmt
         run: test -z "$(gofmt -l .)"
       - name: Hygiene (no panic/reflect/fmt.Print in library code)

docs/design/apt-air-editor.md

@@ -997,7 +997,7 @@ cd "$(dirname "$0")/../webjs"
 node --test airport-editor/**/*.test.js
 ```
 
-- Pin **Node 20 LTS** in CI (`actions/setup-node@v4` with `node-version: "20"`).
+- Pin **Node 24** in CI (`actions/setup-node@v7` with `node-version: "24"`; local floor ≥20).
 - Prefer **zero npm deps** for unit tests (`node:test` only). If `package.json` scripts only, `npm test` can invoke node without `node_modules`.
 - Add `node_modules/` to `.gitignore` if any package is ever added.
 - Update `Agents.md` §9 and CI workflow in **PR 4**.

webjs/README.md

@@ -6,7 +6,7 @@ import via relative paths into the go:embed tree.
 
 ## Requirements
 
-- Node.js **≥ 20** (CI pins Node 20 LTS)
+- Node.js **≥ 20** (CI pins Node 24; floor remains ≥20)
 - Zero production npm dependencies for unit tests (`node:test` / `node:assert/strict`)
 
 ## Run