[skills] Sync vercel-connect with current docs

[vercel-gh-bot-2]

• The Auth.js example connect({ id: "linear", connector: "linear/myagent" }) and the line "Auth.js additionally requires an id" leave out the required name option. In @vercel/connect@2.4.1 (latest), AuthJsConnectOptions in dist/authjs/connect-provider.d.ts declares readonly name: string; with no ?, so the skill's example fails to type-check. The fix adds name: "Linear" to the example and says Auth.js requires an id and a name. Source: https://vercel.com/docs/connect/frameworks/authjs (last_updated 2026-09-18). Its example passes name: 'Linear',, and its options table lists "name | Provider name shown in your sign-in interface."

Verification
run_plugin_checks: build, typecheck, validate, and test all passed (1079 pass, 0 fail).

Test updates
None.

Not changed

• "The SDK supports three subject types" (user, app, jwt-bearer). @vercel/connect@2.4.1 also exports a token-exchange subject, ConnectTokenExchangeSubject ({ type?: 'token'; token: string }). The REST API schema lists it too. The SDK reference and the Tokens concept page still describe three variants and don't say how the token-exchange subject behaves, so the skill was left alone.
• The https://api.vercel.com/v1/connect/token/slack%2Facme-slack link check returned 404. That URL is a POST API endpoint shown as an example, not a docs page.
• The eve entrypoint also exports connectSendblueCredentials, which the skill's list of eve channel helpers doesn't mention. The eve docs page doesn't document Sendblue either, so it was not added.

Opened automatically by the vercel-plugin drift agent. Review before merge.