docs: add synopsis and examples to misc standalone commands

Description

Resolves the remaining smaller standalone-page findings from the style guide audit in #8263 (closed), grouped into one MR.

• Adds a Synopsis to the job, search, token, and user parent commands.
• Adds a Synopsis and Examples to user events and version.
• Adds Examples to completion and auth docker-helper.
• The search command is in beta, so its Synopsis appends the standard text.BetaString note.

Each Synopsis is additive and does not repeat the Short description. The user parent help test was updated to match the rendered Synopsis (Cobra renders Long in place of Short once Long is set).

Commands updated:

• job
• search
• token
• user
• user events
• version
• completion
• auth docker-helper

Content follows the documentation style guide and the GitLab CLI (glab) documentation style guide.

Related issues and merge requests

• docs: Fix CLI documentation inconsistencies ide... (#8263 - closed)

Documentation

If this MR adds or updates CLI command documentation, follow the conventions in the GitLab CLI (glab) documentation style guide, run make gen-docs, and commit the updated files in docs/source/.