[docs-agent] Document discover:defaultEsqlQuery advanced setting

[github-actions]

Adds a "Set a default query" subsection to Use ES|QL in the Kibana UI, under Manage queries, documenting the new discover:defaultEsqlQuery space-level advanced setting: how to set it, its scope, syntax-only validation, when it stops applying, and its priority against a Discover-profile default and the data-source-derived query.

Triage rationale: The issue and linked Kibana PR elastic/kibana#281319 (closing elastic/kibana#281180) together fully specify the behavior: the setting name, its priority order, its syntax-only validation, and that it doesn't apply after a user edits the query or switches modes. The auto-generated advanced settings reference already lists the setting, so this narrative mention was the only missing piece, making the task sufficiently scoped for autonomous handling.

Drafting sources:

• Issue Set a default Discover ES|QL query with an advanced setting #7695 and linked Kibana PR #281319 (implementation evidence)
• explore-analyze/query-filter/languages/esql-kibana.md and explore-analyze/discover/try-esql.md (canonical page and terminology/placement)
• (reference/redacted) (existing auto-generated reference link pattern used elsewhere on the page, e.g. for dateFormat:tzanddiscover:sampleSize`)
• Repository contribute-docs/ style guide and cumulative-docs/applies_to conventions

Reader test: Reader goal — a Kibana admin wanting to override Discover's derived ES|QL query with their own default. 2 rounds. Round 1 surfaced three blocking gaps: no steps for locating the setting, unclear scope of "validates syntax only," and an undefined "Discover session profile" term with no canonical page to link. Round 2 added explicit navigation steps, clarified that syntax-only validation doesn't check whether the query returns results, and replaced the unlinkable term with "a Discover profile provided by your organization." No blocking gaps remained after round 2.

Closes #7695

This draft PR was produced autonomously by docs-agent-experimental in experimental mode.

Safe-output PRs do not trigger CI by default. A maintainer must trigger the required checks manually.

Generated by 🧪 docs-agent-experimental for #7695 · sonnet50 · 43.3 AIC · ⌖ 4.95 AIC · ⊞ 10.2K · ◷

• expires on Aug 21, 2026, 4:04 PM UTC

[florent-leborgne]

Test of the github action

Overall: the steps are correct with a few caveats:

• The change doesn’t warrant a how-to but that would still be acceptable. I think: good 👍
• If we really needed a how to it would have been nice to include prerequisites (to update the advanced setting)
• It gives some internal details that the user can’t set but make it sound like it’s possible
• The applies-to tagging format is incorrect, should have been a section level for a new section
• Didn’t respect the documented pattern for navigating to product pages

What I implement instead: #7869