fix: Remove all Neo4j memory system code to resolve launcher hang (#2148)

Fixes #2144

The launcher was hanging because it imported shutdown_coordinator
which tried to import from amplihack.memory.neo4j.lifecycle - but
that directory was missing from the installed package.

Changes:
- Removed Neo4j startup code from session_start hook (replaced with no-op)
- Removed Neo4j test marker from pytest.ini and pyproject.toml
- Removed Neo4j backend detection from auto_backend.py
- Updated hooks to use Kuzu-only memory system
- Deleted 14 Neo4j test scripts from scripts/ directory
- Updated historical comments in Kuzu files to avoid mentioning removed code

All active Neo4j code has been removed. Kuzu remains as the sole memory backend.

Co-authored-by: Ubuntu <azureuser@amplihack-dev.ftnmxvem3frujn3lepas045p5c.xx.internal.cloudapp.net>
Co-authored-by: Claude Sonnet 4.5 (1M context) <[email protected]>

Author: 3 people

.claude/AMPLIHACK.md

@@ -25,6 +25,7 @@ When starting a session, import these files for context:
 ### When to Classify
 
 Classify when the user:
+
 - **Starts a new topic** (different domain/goal from current work)
 - **First message of the session** (no prior context)
 - **Explicitly changes direction** ("Now let's...", "Next I want...", "Different question...")
@@ -33,6 +34,7 @@ Classify when the user:
 ### When NOT to Re-Classify
 
 Do NOT re-classify when the user:
+
 - **Asks follow-ups** ("Also...", "What about...", "And...")
 - **Provides clarifications** ("I meant...", "To clarify...")
 - **Requests related additions** ("Add logout too", "Also update the tests")
@@ -73,12 +75,12 @@ Following: .claude/workflow/[WORKFLOW_NAME].md
 
 **Default Behavior**: Claude invokes ultrathink-orchestrator for non-trivial development and investigation tasks.
 
-| Task Type         | Claude's Action        |
-| ----------------- | ---------------------- |
-| **Q&A**           | Responds directly      |
-| **Operations**    | Responds directly      |
-| **Investigation** | Invokes /ultrathink    |
-| **Development**   | Invokes /ultrathink    |
+| Task Type         | Claude's Action     |
+| ----------------- | ------------------- |
+| **Q&A**           | Responds directly   |
+| **Operations**    | Responds directly   |
+| **Investigation** | Invokes /ultrathink |
+| **Development**   | Invokes /ultrathink |
 
 **Task classification**: See "Classification Keywords" section above for keyword triggers.