Attribute rich text editor specs to the markdown category

What does this MR do and why?

The rich text editor - * shared examples cover app/assets/javascripts/content_editor (groupknowledge), but they inherit the feature_category of whichever spec includes them. There is no single host — they are pulled into seven spec files across three unrelated categories:

Host spec	Category it reports under today
work_items/issues/new/user_creates_issue_spec.rb	team_planning
work_items/issues/user_comments_on_issue_spec.rb	team_planning
merge_request/user_edits_merge_request_spec.rb	code_review_workflow
merge_request/user_comments_on_merge_request_spec.rb	code_review_workflow
projects/wiki_spec.rb (via the wiki shared examples)	wiki
ee/.../groups/wiki_spec.rb (via the wiki shared examples)	wiki

So a content editor regression is routed to whichever team happens to host the examples. This MR tags the groups and examples inside the shared example blocks so the category travels with them into every host, present and future:

  describe 'autocomplete suggestions', feature_category: :markdown do

18 declarations across the 8 files — every top-level describe/context, plus the three loose examples in common_shared_examples.rb.

Why not on the RSpec.shared_examples declaration

RSpec.shared_examples 'rich text editor - autocomplete', feature_category: :markdown looks like the obvious place, but it is wrong here, in two ways.

The suite leaves shared_context_metadata_behavior at RSpec's default of :trigger_inclusion. Under that mode, metadata on a shared group means "include these examples into every group carrying this metadata" — it would inject the entire rich text editor suite into all 156 specs tagged feature_category: :markdown. Verified:

some other markdown-tagged spec example FROM the shared group    fc=:markdown   # never asked for it

And it does not even achieve the goal: the group that genuinely calls it_behaves_like still reported fc=:team_planning.

it_behaves_like 'rich text editor - autocomplete', feature_category: :markdown does not work either — extra arguments are forwarded to the shared example block as parameters, so the category is unchanged and the block's params default is overridden, silently dropping seven examples.

Verified

Per-example feature_category is what gets reported (spec/support/formatters/json_formatter.rb). Dry-run through that formatter, before and after, across three hosts with three different categories:

Host spec	before	after
user_creates_issue_spec.rb	86 team_planning	24 team_planning + 62 markdown
user_edits_merge_request_spec.rb	20 code_review_workflow	10 code_review_workflow + 10 markdown
wiki_spec.rb	180 wiki	153 wiki + 27 markdown

Totals conserved, so no example was missed by tagging at group level. No spec files moved, no examples added or removed, and no example names changed.

Also confirmed no accidental auto-inclusion: spec/features/markdown/ specs report 26 examples both before and after.

References

• Flaky test issue: https://gitlab.com/gitlab-org/quality/test-failure-issues/-/work_items/43774