feat(examples): add examples-migrate tool

[Timothee Guerin (timotheeguerin)]

Part of the Unified Examples Format epic (#4831), tracking #4833.

Stack

• feat(examples): add examples.yaml JSON schema and examples-validate tool #4908 — examples.yaml schema + examples-validate (base)
• This PR → examples-migrate (base: examples-file-format)
• examples-resolve (stacked on top of this)

Stacked PR — review/merge after the PR below it. Targets examples-file-format, not main.

What

Adds the examples-migrate tool + examples-migrate CLI to @azure-tools/typespec-azure-examples, which converts versioned Swagger x-ms-examples into the unified examples.yaml format.

• Operation key derived by splitting operationId on the first _ and lowercasing the method segment (e.g. CaCertificates_Get → CaCertificates.get).
• De-duplicates example variants across API versions into since-anchored lineages.
• Emits examples.yaml (bare integer status keys, quoted since, single-file or per-interface split).

Tests added (vitest); tsc, oxlint, prettier clean.

[microsoft-github-policy-service]

Hi @Timothee Guerin (@timotheeguerin). Your PR has had no update for 14 days and it is marked as a stale PR. If it is not updated within 14 days, the PR will automatically be closed. If you want to refresh the PR, please remove the stale label.