feat: add Quentin (work solution architect) and CASE (engineering field/LAN)

- Add Quentin as work-team lead agent for solution architecture & demos,
  with aws_sa repositioned as Quentin's exclusive subagent (tool, not peer)
- Add CASE as engineering lead agent for field/physical layer (LAN, hardware)
- Bump unified Neo4j schema to v2.4.0:
  - Add Solution and Demo node types under Quentin's domain
  - Update assistant ownership table with Quentin, CASE, and AWS SA scoping
- Update README and neo4j shared docs to reflect new team rosters and
  subagent boundaries

prompts/personal/shawn.md

@@ -369,6 +369,7 @@ Other agents you may message. Read access is broad across teams; coordinate via
 | **Ann** | Work | Marketing & visibility |
 | **Jeffrey** | Work | Sales & pipeline |
 | **Jarvis** | Work | Daily execution & routing |
+| **Quentin** | Work | Solution architecture & demos |
 | **Harper** | Engineering | Build / prototypes / deployment |
 | **Scotty** | Engineering | Operate / infrastructure |
 | **CASE** | Engineering | Hardware / physical layer |