[TypeSpec Authoring][Benchmark] Add checkExistence(HEAD) operation to existing resource case

[JoyerJin]

No description provided.

[Copilot]

Pull request overview

Adds a new benchmark stimulus (002011-arm-add-check-existence-operation) that exercises the azure-typespec-author skill's ability to add a checkExistence (HEAD) operation to an existing ARM resource, registers it in the armtemplate suite, and provides both a standalone eval file and an entry in the consolidated eval.yaml.

Changes:

• New standalone eval evals/002011.eval.yaml defining the stimulus, fixtures, graders (tool-calls, skill-invocation, file-matches on ArmResourceCheckExistence<Employee>, prompt) and scoring weights.
• Added the same stimulus to the aggregated evals/eval.yaml under the armtemplate tag.
• Wired the new eval into .vally.yaml's armtemplate suite list.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
.github/skills/azure-typespec-author/evaluate/evals/002011.eval.yaml	New standalone Vally eval for the checkExistence stimulus.
.github/skills/azure-typespec-author/evaluate/evals/eval.yaml	Adds the same stimulus to the aggregated multi-stimulus eval.
.github/skills/azure-typespec-author/evaluate/.vally.yaml	Registers the new eval file in the armtemplate suite.