[DE][9.4 & Serverless] Attach Security Detection rule as AI Agent context

[nastasha-solomon]

Summary

Fixes #5364.

Documents the Add to chat feature that lets users attach a Security detection rule to the AI Agent from rule details, rule editing, rule creation, and alert flyouts.

• New section "Attach a detection rule to the AI Agent" highlights the following:
  • Where Add to chat appears (rule details, rule editing, rule creation, alerts flyout rule summary, alerts table rule flyout).
  • What the agent can help with (detection intent, query logic, MITRE ATT&CK coverage, timing/scheduling, metadata quality, investigation guide suggestions).
  • What the agent can "see" -- only rule-defined fields. Also does not resolve exception lists.
• Added a note after the "Edit a single rule" section. Highlights that Add to chat is available from the rule details page and edit rule settings view.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

Cursor + Auto

[github-actions]

Vale Linting Results

Summary: 2 suggestions found

💡 Suggestions (2)

File	Line	Rule	Message
solutions/security/ai/agent-builder/agent-builder.md	27	Elastic.Clone	Use clone only when referring to cloning a GitHub repository or creating a copy that is linked to the original. Often confused with 'copy' and 'duplicate'.
solutions/security/ai/agent-builder/agent-builder.md	50	Elastic.Semicolons	Use semicolons judiciously.

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[github-actions]

🔍 Preview links for changed docs

• solutions/security/ai/agent-builder/agent-builder.md
• solutions/security/detect-and-alert/manage-detection-rules.md
• solutions/security/detect-and-alert/validate-and-test-rules.md

[benironside]

Your work LGTM @nastasha-solomon! I added a section to the Validate and test your detection rules page about how to validate rules using AI. Please lmk what you think!