Add field presenter variant concept for context-aware rendering

What does this MR do and why?

Adds a field presenter variant concept for context-aware rendering in list displays. This is the third MR in a stack that adds CodeSuggestion analytics support to the GitLab UI.

What Changed

• FieldPresenter variant prop: added a variant prop to FieldPresenter that allows presenter resolution to be context-aware. The presentersByFieldKey map now supports variant keys (lowercase, e.g. compact) alongside typename keys (PascalCase). Variant matches take precedence over typename matches, with default as the fallback. For example, the user field key uses UserAvatarPresenter when the item typename is DuoCodeSuggestionsAggregationResponseDimensions, but the compact variant overrides this to use UserPresenter instead.
• ListPresenter: conditionally renders a title heading only when a title field is present (supporting analytics data which has no title), and passes variant="compact" to field presenters for non-title fields
• DataPresenter: removed the mode prop and analytics-specific routing, since ListPresenter now handles both standard and analytics list displays through the variant mechanism

MR Stack

1. !233396 (merged) — Backend + GLQL pipeline
2. !233397 (merged) — Analytics presenters
3. This MR — Field presenter variants for context-aware list rendering

References

• GLQL UI integration for CodeSuggestion analytics (#592262)
• Add CodeSuggestions support to GLQL in GitLab UI (!228129 - closed)
• GLQL MR !347 (Analytics Infrastructure)
• GLQL MR !348 (CodeSuggestions Source)
• Work Item 592262
• ClickHouse Setup Documentation
• GLQL User Documentation

Screenshots or screen recordings

Scenario	GLQL query	Output
Every metric and dimension - list
Every metric and dimension - ordered list
In the Data Analyst Agent	Requires a lot of cajoling until Data Analyst agent integration for CodeSuggesti... (#592264) is complete
With feature flag disabled
Trying to use it outside analytics mode
Trying to use fields
Trying to use dimensions or metrics in standard mode

How to set up and validate locally

Prerequisites

• Setup clickhouse
• Make sure to run migrations: bundle exec rake gitlab:clickhouse:migrate
• Enable clickhouse analytics: echo "Gitlab::CurrentSettings.current_application_settings.update(use_clickhouse_for_analytics: true)" | rails c
• Seed test data: FILTER=ai_usage_stats bundle exec rake db:seed_fu

UI Testing

1. Navigate to a seeded projects issue or merge request (by default this is the toolbox group), and go to a markdown enabled field (comments or descriptions for instance)

2. Test that without the feature flag enabled, the CodeSuggestion type returns an error:

   mode: analytics
   display: orderedList
   query: type = CodeSuggestion and timestamp >= -30d
   dimensions: language
   metrics: totalCount, acceptanceRate
   sort: totalCount desc
   limit: 10

3. Enable the feature flag: echo "Feature.enable(:glql_code_suggestion_analytics_aggregation)" | rails c

4. Refresh the page, test that the query no longer errors and returns results

5. Now test other variants like: Ide comparison by language

   mode: analytics
   display: list
   query: type = CodeSuggestion and language in ("ruby", "javascript", "python")
   dimensions: language, ideName
   metrics: totalCount, acceptedCount, rejectedCount, acceptanceRate
   sort: acceptanceRate desc

   Recent activity

   mode: analytics
   display: orderedList
   query: type = CodeSuggestion and timestamp >= -7d
   dimensions: language
   metrics: totalCount, usersCount, suggestionSizeSum
   sort: usersCount desc
   limit: 5

   User-specific

   mode: analytics
   display: list
   query: type = CodeSuggestion and user = 2 and timestamp >= -14d
   dimensions: language, ideName
   metrics: totalCount, acceptanceRate, acceptedCount
   sort: totalCount desc

6. Also verify that percentage presenters like acceptanceRate show as percentages

7. Also verify that number presenters like totalCount format according to your browser language (e.g. 1,234 or 1.234)

Rest API endpoint

Test the /api/v4/glql REST API endpoint:

# Get a personal access token from GitLab UI: User Settings > Access Tokens

curl -H "PRIVATE-TOKEN: your_token" \
  -H "Content-Type: application/json" \
  -d '{
    "glql_yaml": "query: type = CodeSuggestion and language = \"ruby\"\nmode: \"analytics\"\ndimensions: \"language\"\nmetrics: \"totalCount, acceptanceRate\"\nproject: \"toolbox/gitlab-smoke-tests\""
  }' \
  http://gdk.test:8080/api/v4/glql