[Bug]: typespec-ts modular-unit snapshots stale after ARM doc changes in #4494 — CI red on main

[xirzec]

Describe the bug

packages/typespec-ts unit-modular scenario snapshots are stale on main, causing the typespec-ts / CI → Run unit tests job to fail for any PR that touches packages/typespec-ts/** (the pull_request build merges main, so the stale snapshots are exercised against the current ARM library).

Root cause: #4494 ("Improve documentation for ARM library decorators, interfaces, and models") changed the ARM operation templates in packages/typespec-azure-resource-manager/lib/*.tsp — the human-facing operation docs (e.g. A long-running resource action.) were moved to @dev and the public doc set to @doc(""). As a result ARM LRO operations now emit no public doc comment. The checked-in typespec-ts modular-unit scenario snapshots still expect the old doc text, so the generated output no longer matches.

Because #4494 did not touch packages/typespec-ts/**, ci-typescript.yml never ran on it, so the snapshot drift landed on main unnoticed. The merge_group runs for pr-4494 and pr-4547 show the same failure on the queue.

Example diffs from the failing job:

- /** A long-running resource action. */ export function backup(
+ export function backup(

- /** * This sample demonstrates how to a long-running resource action. * * @summary a long-running resource action. ...
+ /** * This sample demonstrates how to * * @summary * ...

Affected scenarios include (at least) the ARM samples/operations that use ArmResourceActionAsync-style templates, e.g. test/modular-unit/scenarios/samples/parameters/bodyOptionalParameterName.md and test/modular-unit/scenarios/operations/lroPaging.md.

Suggested fix: regenerate the affected modular-unit snapshots against current main by running the unit tests with the update flag, then commit the updated .md scenario files:

cd packages/typespec-ts
SCENARIOS_UPDATE=true pnpm unit-test

Broader follow-up to consider: ARM library (typespec-azure-resource-manager) changes can alter typespec-ts emitted output but do not currently trigger ci-typescript.yml, so this class of drift can recur. Consider widening the ci-typescript.yml paths triggers to include the emitter's TypeSpec library dependencies (e.g. typespec-azure-resource-manager, typespec-client-generator-core) and/or reconsidering which suites run in the repo-wide vitest run.

Context: found while working on #4788 (enabling typespec-ts unit tests in the repo-wide run). That PR is currently red solely due to this pre-existing drift, not its own changes.

Reproduction

Not a spec/playground bug — this is a repo CI / snapshot drift issue reproducible in the repo itself:

1. Check out current main (which includes Improve documentation for ARM library decorators, interfaces, and models #4494).
2. pnpm install and build typespec-ts and its dependencies.
3. cd packages/typespec-ts && pnpm unit-test.
4. Observe AssertionError snapshot mismatches for ARM LRO operations/samples where the expected output contains doc comments (e.g. A long-running resource action.) that the current ARM library no longer emits.

Checklist

• Follow our Code of Conduct
• Check that this issue is about the Azure libraries for typespec
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• The provided reproduction is a minimal reproducible example of the bug.