DOCS-12 - Refactor release note templates: remove marketing language, add tag taxonomy

[kimsauce]

Purpose of this pull request

Two related improvements to release note templates and style guidance:

1. Remove marketing language. Removes excitement/announcement openers ("We're excited to introduce", "We are excited to announce") from release note templates, style guide, and the sumo-style skill. Replaces them with direct factual statements. Real examples used as the do/don't reference:

• ❌ "We're excited to announce that multi-child-org search results now include an _orgName field..."
• ✅ "Multi-child-org search results now include an _orgName field alongside _orgId..."

2. Add tag taxonomy. Adds tags: frontmatter to all five release note skill templates so new posts are tagged from the start. Tags create filterable index pages (for example, /release-notes-service/tags/ai/) for easier category navigation. Tags are applied to new posts going forward only — no backfill.

Blog	Tags
Service	apps manage search ui alerts security ai
Collector	installed-collector opentelemetry-collector
CSE	cloud-siem + rules / log-mappers / parsers
CSOAR	cloud-soar + integrations / playbooks / automation-service
Developer	api deprecation cli

Select the type of change

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions, updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - .clabot, version updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

Ticket (if applicable)

https://sumologic.atlassian.net/browse/DOCS-12