docs: add synopsis and examples to issue and incident commands

Description

Resolves the issue and incident family findings from the style guide audit in #8263 (closed). These two families are grouped because they share the issuable command builders (for example, issue note and incident note are both produced by internal/commands/issuable/note).

• Adds a Synopsis to the issue, issue board, and incident parent commands.
• Adds a Synopsis to issue board create, issue board view, issue create, issue delete, and issue update.
• Adds Examples to issue board create, issue board view, issue note, and incident note. The note Examples come from the shared issuable/note builder, so the same change covers both pages.
• Adds a Synopsis note to issue create explaining that the --recover flag is experimental and not ready for production use.

Each Synopsis is additive and does not repeat the Short description. The issue, issue board, and incident parent help tests were updated to match the rendered Synopsis (Cobra renders Long in place of Short once Long is set).

The --output-format / -O flags on issue list and incident list are intentionally left unchanged here (a previous output-flag MR for those pages was closed), and the --in flag-capitalization fix on those pages is handled separately in the quick-wins MR.

Commands updated:

• issue, issue board, issue board create, issue board view, issue create, issue delete, issue update, issue note
• incident, incident note

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/.