Implement coder task create (alias run) to create and run a task.

Scope

• Usage: coder task create <template-or-recipe> --name <str> [--input <text> | stdin] [--wait] [--wait-timeout <dur>] [--param k=v]...
• MVP <template-or-recipe>: <template-uuid> or <template-name>[@version]. Defer recipes (<recipe-uuid>, :<recipe-name>) to post-MVP.
• Support --input (alias --prompt) from flag or stdin.
• --wait blocks until status is idle or completed and streams logs while waiting.
• If --name omitted, backend generates a name.
• Calls POST /tasks (maps input to prompt parameter).
• Include minimal SDK surface + tests.

Depends on: #893, #898

References: #838