Add and normalize Streams frontmatter descriptions across 11 docs pages

[Copilot]

This PR addresses frontmatter quality gaps in /solutions/observability/streams by adding missing description metadata and replacing one weak “Learn how …” description pattern. The goal is to ensure all flagged pages have schema-compliant, concise descriptions.

• Frontmatter completeness fixes (10 files)

  • Added missing description fields to:
    • management/advanced.md
    • management/data-quality.md
    • management/extract.md
    • management/partitioning.md
    • management/retention.md
    • management/schema.md
    • management/significant-events.md
    • management/streamlang.md
    • streams.md
    • wired-streams.md

• Description quality normalization (1 file)

  • Updated management/knowledge-indicators.md description to remove the weak “Learn how …” phrasing while preserving meaning.

• Description constraints alignment

  • All updated descriptions are non-empty and within the 200-character limit required by the repo’s frontmatter expectations.

Example of the applied pattern:

---
applies_to:
  serverless: ga
  stack: preview =9.1, ga 9.2+
description: Streams provides a centralized UI for extracting fields, setting retention, routing data, and managing Elasticsearch data streams.
products:
  - id: observability
---

[github-actions]

Elastic Docs AI PR menu

Check the box to run an AI review for this pull request.

• Review docs changes (docs-review). Status: not started.

Powered by GitHub Agentic Workflows and docs-actions. For more information, reach out to the docs team.