[docs-agent] Document CPS-eligible tier gating for space project routing panel

[github-actions]

Summary

Adds a note to Manage access and scope for cross-project search explaining that the Cross-project search panel in space settings (create space and edit space pages) only appears for projects on a CPS-eligible pricing tier, and that a downgraded space retaining a non-default project routing value keeps the panel visible until the scope is reset to All projects. The tier requirements are cross-linked to the existing "projects available for linking" section rather than duplicated.

Triage rationale

The issue (#7635) was sufficiently specified: it names the exact page/section to edit, the exact behavior to document, and links Kibana PR elastic/kibana#278267. I verified the behavior directly against that PR's diff — specifically edit_space_general_tab.tsx's canReadProjectRouting(), which now checks cps?.isTierEligible === true || isCustomProjectRouting(space.projectRouting) — confirming both the tier-gating and the downgrade escape-hatch behavior described in the issue. The new CPS_TIER_ELIGIBLE_FEATURE in kbn-cps-common/pricing.ts confirms eligible tiers are Security/Observability Complete, matching the tier requirement already documented in cross-project-search-config.md#cps-compatibility, so the fix cross-links instead of restating the tier list.

Drafting sources

• Repo-local: AGENTS.md (cumulative docs, style, canonical-page principles)
• Existing page: deploy-manage/cross-project-search-config/cps-config-access-and-scope.md
• Existing page: deploy-manage/cross-project-search-config.md (#cps-compatibility tier requirements, reused via cross-link)
• Implementation evidence: elastic/kibana#278267 diff for edit_space_general_tab.tsx and kbn-cps-common/src/common/pricing.ts

Note: The Elastic Docs MCP server (elastic-docs) returned no available tools in this run, so contribution guidance was drawn from the repository's local AGENTS.md/contribute-docs content instead.

Reader test

• Reader goal: An Elastic Cloud Serverless administrator managing Kibana spaces, trying to set the default CPS scope and understand why the panel might not appear.
• Rounds: 1
• Result: No blocking comprehension gaps in the new content. The reader tester flagged one pre-existing, unrelated gap (how to navigate to the "Cross-project search" page) that predates this change and is out of scope for this issue.

Closes #7635

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 #7635 · sonnet50 · 43.2 AIC · ⌖ 4.92 AIC · ⊞ 10.2K · ◷

• expires on Aug 21, 2026, 3:55 PM UTC