ci: bump actions/setup-node version to avoid regression

[xiashtra]

• Require actions/setup-node to use Node version >=24.18.0 to avoid a bug introduced in 24.17 (http: node-fetch throws ERR_STREAM_PREMATURE_CLOSE on keep-alive socket closures after latest security releases nodejs/node#63989)
• lint-pr-title updated to use actions/checkout@v6 (missed in ci: Update actions to latest versions #1057)

[Legends0]

This might have broken the timeline test?

EDIT: Nevermind, problem went away after updating the PR branch.

This is what I saw:

> cactbot@0.37.3 test
> mocha

(node:3199) ExperimentalWarning: `--experimental-loader` may be removed in the future; instead use `register()`:
--import 'data:text/javascript,import { register } from "node:module"; import { pathToFileURL } from "node:url"; register("ts-node/esm", pathToFileURL("./"));'
(Use `node --trace-warnings ...` to show where the warning was created)
file:///home/runner/work/cactbot/cactbot/node_modules/yargs/yargs:3
const {applyExtends, cjsPlatformShim, Parser, Yargs, processArgv} = require('./build/index.cjs')
                                                                    ^

ReferenceError: require is not defined in ES module scope, you can use import instead
    at file:///home/runner/work/cactbot/cactbot/node_modules/yargs/yargs:3:69
    at ModuleJobSync.runSync (node:internal/modules/esm/module_job:551:37)
    at ModuleLoader.importSyncForRequire (node:internal/modules/esm/loader:346:47)
    at loadESMFromCJS (node:internal/modules/cjs/loader:1762:24)
    at Module._compile (node:internal/modules/cjs/loader:1926:5)
    at Object..js (node:internal/modules/cjs/loader:2084:10)
    at Module.load (node:internal/modules/cjs/loader:1666:32)
    at Module._load (node:internal/modules/cjs/loader:1447:12)
    at wrapModuleLoad (node:internal/modules/cjs/loader:260:19)
    at Module.require (node:internal/modules/cjs/loader:1689:12)

Node.js v26.4.0

[xiashtra]

Node.js v26.4.0

This run pulled in Node 26, which may have breaking changes. I'm not sure why it grabbed this version, instead of the current LTS version of 24.18.0; setup-node is supposed to pull LTS versions unless directed otherwise. We should keep an eye out for this happening again.