React to alert, attack, and note changes with new workflow triggers

## Summary

Adds 8 new event-driven workflow triggers under the security.* namespace so workflows can react when alert or attack status, tags, or assignees change, or when timeline notes are created or updated. This is the foundational plumbing enabling Security Solution to participate in the workflows event-trigger platform, following the same architecture already used by Cases.

**Why this needs docs:** release_note:feature adding a brand-new family of 8 workflow triggers (alertStatusChanged, alertTagsChanged, alertAssigneesChanged, attackStatusChanged, attackTagsChanged, attackAssigneesChanged, noteCreated, noteUpdated), none of which appear anywhere on the Event-driven triggers reference page, which currently only documents workflows.failed, Cases, entity store, and experimental alerting system triggers.

## Resources

- PR [#285106](https://github.com/elastic/kibana/pull/285106) — [Security Solution] Add event-based workflow triggers for alert, attack, and note mutations
- Also applies to: Security - Threat Hunting

## Availability

| Channel | Details |
|---------|---------|
| **Stack** | v9.6.0 |
| **Serverless** | Aug 31–Sep 4 |
| **Feature flag** | None — active by default |

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## Suggested edits

[Event-driven triggers](https://www.elastic.co/docs/explore-analyze/workflows/triggers/event-driven-triggers) > (new) Security triggers
- **What the docs say:** Page lists workflows.failed, Cases triggers, Entity store triggers, and experimental alerting system triggers only — no security.* alert/attack/note triggers exist on the page.
- **What to add:** Add a new 'Security triggers' section documenting the 8 security.* trigger IDs (alertStatusChanged, alertTagsChanged, alertAssigneesChanged, attackStatusChanged, attackTagsChanged, attackAssigneesChanged, noteCreated, noteUpdated), their schemas, event payload fields, the MAX_ALERTS_PER_TRIGGER truncation behavior for by-query triggers, and example conditions, mirroring the existing Cases triggers pattern. Applies from 9.6.0 and in serverless.