Add dedicated CLI reference page to RedisVL docs

[tylerhutcherson]

Summary

Add a dedicated CLI reference section to docs that covers command syntax, options, and practical examples.

Level: Beginner

Current State

• docs/user_guide/cli.ipynb exists, but there is no API-style CLI reference page in docs/api/.
• Users must piece together command capabilities from notebooks and source code.

Proposed Change

• Add a dedicated CLI docs page (for example docs/api/cli.rst or docs/user_guide/cli_reference.md).
• Document command groups and subcommands with:
  • usage syntax
  • required/optional flags
  • examples for common workflows
  • expected output/error behavior
• Link this page from docs/user_guide/index.md and docs/index.md.

Definition of Done

• A discoverable CLI reference page is included in docs navigation.
• Core rvl commands are covered with tested examples.
• make docs-build passes.

Out of Scope

• CLI feature implementation changes (documentation only).