[Base] Add typed Field Groups shortcut

Summary

Add a typed Base shortcut for creating Field Groups (column groups in the Base UI). This is distinct from record grouping through +view-set-group.

Environment

• lark-cli: 1.0.81
• Brand: Lark
• Identity tested: user

Current behavior

lark-cli base --help exposes field CRUD and view grouping, but no +field-group-* shortcut. Agents must use the raw API escape hatch:

lark-cli api POST /open-apis/bitable/v1/apps/<app_token>/tables/<table_id>/field_groups \
  --as user \
  --data @field-groups.json

The endpoint works when the token has base:field_group:create. It is also represented by AppTableFieldGroup.Create in the official Go SDK.

Proposed behavior

Provide a typed shortcut such as:

lark-cli base +field-group-create \
  --base-token <app_token> \
  --table-id <table_id> \
  --json @field-groups.json \
  --as user \
  --dry-run

The shortcut should:

• Declare and check base:field_group:create.
• Validate the top-level field_groups array and non-empty children.
• Explain that each field can belong to only one Field Group.
• Surface error 1254122 as an existing/duplicate group membership conflict.
• Clearly distinguish Field Groups from +view-set-group.
• Return the created field_groups[].id, name, and description.

If the platform only exposes create today, the CLI should not invent unsupported list/update/delete operations.

References

• Official SDK sample: https://github.com/larksuite/oapi-sdk-go/blob/v3_main/sample/apiall/bitablev1/create_appTableFieldGroup.go
• Endpoint: POST /open-apis/bitable/v1/apps/:app_token/tables/:table_id/field_groups

Start by tracing the existing Base field CRUD shortcuts and their help and validation patterns, then compare the official Go SDK Field Group sample with the documented POST endpoint. Add only the typed create shortcut, including permission and payload checks, duplicate-membership error handling, distinction from +view-set-group, and created field-group output. Done when the proposed dry-run command and relevant help behavior work without inventing unsupported operations.