[CahidArda]

Adds upstash redis create-branch --db-id <source-id> --name <name>, which creates a branch of a Redis database: a point-in-time copy with its own endpoint and password (CLOUD-4877, upstash/upstash-console-v2#1611, upstash/upstash-cloud#3926).

A branch is an ordinary database record with its own ID, so this is the only new command. redis list shows branches with root_database_id set, redis get shows when one is ready (state goes from creating to active), and redis rename and redis delete work on them by ID.

Changes

• New redis create-branch, which posts to POST /v2/redis/database/:id/branch and prints the branch as JSON.
• README quick examples show the command; the docs reference is in upstash/docs (DX-3274).
• Database type gains root_database_id and source_database_id.

Testing

New unit test covers the route, method, body and output. 173 unit tests and the typecheck pass, and create-branch --help renders from a build. The API response is mocked: no branch was created against production.

[linear-code]

DX-3274