[TCGC] Require explicit union hierarchies - #5561

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020, pnpm/action-setup@eae0cfeb286e66ffb5155f1a79b90583a127a68b. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

{ "workflowData": { "owner": "Azure", "repo": "typespec-azure", "sha": "ec593edb19e9ae7398adc96d3c323106f141f3f7", "ref": "5561", "headBranch": null }, "key": "VHM0L2ihsl", "runId": 36633401964, "webhookDebug": { "action": "requested", "head_branch": "joshlove-msft-union-extends-inheritance", "head_repository_full_name": "JoshLove-msft/typespec-azure", "full_name": "Azure/typespec-azure", "isPullRequest": true, "prNumber": 5561, "prNumberType": "number", "isNewPullRequest": true, "isOldPullRequest": false, "prKey": "JoshLove-msft/typespec-azure:joshlove-msft-union-extends-inheritance", "oldPrDataHash": "4S3GzKnChB", "lookupKey": "JoshLove-msft/typespec-azure:joshlove-msft-union-extends-inheritance", "data": { "owner": "Azure", "repo": "typespec-azure", "sha": "ec593edb19e9ae7398adc96d3c323106f141f3f7", "ref": "5561", "headBranch": null } }, "currentCursor": { "sha": "471afba0ab25669e4b8b9827f49a1ac3011bcb32", "timestamp": 36037206982 }, "pkgPrNewVersion": "0.0.88" }