[Docs] Clarify the introduction's platform, agent, and CLI artifact count

## Location docs/introduction.md, The two deliverables ## Problem The section is titled The two deliverables and says DockSight ships as two independent products, but the next paragraph introduces a third artifact, the CLI. This makes the release model confusing for new contributors. ## Correction Rewrite the section so it clearly distinguishes: - the platform artifact; - the agent artifact; - the CLI artifact that installs and updates the other two. Use the same terminology as docs/release-process.md and avoid calling the platform and agent products if that conflicts with the repository's release model. ## Acceptance criteria - The heading and body agree on whether there are two products and three artifacts. - Platform, agent, and CLI responsibilities are unambiguous. - Links to release-process documentation remain correct. - Documentation-only change.