add OS + Pro Engagement articles (#14583)

* add OS + Pro Engagement articles

* update file title for linux builds

* change naming for linux -- again

* add jira content

* fix links

* docs: fix broken jira_guide links in engagement articles

The new engagement docs linked to /issue_tracking/jira/jira_guide, but the
actual pages are split into os__jira_guide and pro__jira_guide. Lychee
flagged six broken links across the OS and Pro variants.

Also drop the -for-products suffix on the Pro-side epic-mapping anchor —
the Pro guide's heading is "Enable Engagement Epic Mapping" without the
parenthetical that the OS guide carries.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Paul Osinski <posinski34@gmail.com>
Co-authored-by: Paul Osinski <42211303+paulOsinski@users.noreply.github.com>
Co-authored-by: Cody Maffucci <46459665+Maffooch@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 4 people