Bump to v19.0.0 (Security Auditor, Personas & Catalog) (#36)

- package.json -> 19.0.0
- README badge + "What's New in v19.0.0" (v18 collapsed), latest-release line
- CHANGELOG: promote [Unreleased] -> [19.0.0] with compare links
- SECURITY.md supported-versions table

Ships the security auditor, personas, orchestration guide, docs catalog, and
roadmap to npm on publish.


Claude-Session: https://claude.ai/code/session_016JWn5jRD5tcEFKrubjQ6Px

Co-authored-by: Claude <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pm-claude-skills",
-  "version": "18.0.0",
+  "version": "19.0.0",
   "type": "module",
   "description": "167 professional Agent Skills (SKILL.md) + subagents + slash commands for Claude, ChatGPT, Gemini, Cursor, Codex & Hermes. Install into any AI coding tool with: npx pm-claude-skills add --agent <tool>.",
   "keywords": [