ci: bump npm publish jobs to Node 24 (npm@latest EBADENGINE)

[pgrayy]

What

Bump node-version from 20 to 24 in the two npm publish jobs (node-publish-platform and node-publish-main) in release.yml.

Why

The publish jobs set up Node 20 and then run npm install -g npm@latest. The current npm@12.0.1 declares engines: { node: "^22.22.2 || ^24.15.0 || >=26.0.0" } and dropped Node 20, so every npm publish now fails immediately with:

npm error code EBADENGINE
npm error notsup Required: {"node":"^22.22.2 || ^24.15.0 || >=26.0.0"}
npm error notsup Actual:   {"npm":"10.8.2","node":"v20.20.2"}

This broke the npm side of the 0.3.0 release: all 5 node-publish-platform matrix jobs failed and node-publish-main was skipped. PyPI published fine, so 0.3.0 currently exists on PyPI but npm is still on 0.2.0 (see run 29584633292).

Change

• node-publish-platform: node-version: "20" → "24"
• node-publish-main: node-version: "20" → "24"

Build/CI jobs are intentionally left on their current Node version. They don't run npm install -g npm@latest, so they aren't affected.

Verification

• Static: release.yml parses as YAML; bump scoped to the two publish jobs, CI/build jobs still on Node 20.
• Reproduced fix: on the exact Node 24.15.0 this pins, npm install -g npm@latest succeeds → npm 12.0.1 (the version that threw EBADENGINE on Node 20). EXIT: 0, no engine error. (Note: Node 25 does not satisfy ^22.22.2 || ^24.15.0 || >=26.0.0 either, so 24 is the correct pin.)
• Publish path: npm publish --dry-run under Node 24 on the real 0.3.0 tarballs (incl. win32-x64-msvc) runs clean through packaging + integrity + the dry-run registry step. No errors.
• Not covered: the OIDC registry upload itself. Final confirmation is a real publish on Node 24 when the 0.3.0 npm side is reconciled after merge.

After merge

Re-dispatch 0.3.0 to publish @strands-agents/shell to npm and reconcile the split-publish state (PyPI + git tag already at 0.3.0).