fix: address markdown lint and doc accuracy issues (threads 6-13)

Thread 6: Add python language specifier to .claude-plugin/README.md code fence
Thread 7: Fix MD022/MD031 spacing in docs/MARKETPLACE.md
Thread 8: Blank line before Destructive Actions heading in README.md
Thread 9: Move H1 to first line in skills/unraid/references/api-reference.md
Thread 10+11+12: Rewrite quick-reference.md:
  - Fix MD022/MD031 (blank lines around headings/fences)
  - Add python language specifiers to all code fences
  - Fix disk/logs params: path/lines → log_path/tail_lines
  - Add path param to live/log_tail example
  - Remove invalid notification/unread subaction
  - Fix notification/list filter= → list_type=
Thread 13: Add python/text language specifiers to troubleshooting.md fences
Thread 14: Update test-tools.sh header comment (in separate commit)
Also: Remove 'connect' from README system subactions table (it was removed from
the tool in previous commit), fix notification 'unread' → 'mark_unread' in table

.claude-plugin/README.md

@@ -49,7 +49,7 @@ Query and monitor Unraid servers via GraphQL API - array status, disk health, co
 
 After installation, run setup to configure credentials interactively:
 
-```
+```python
 unraid(action="health", subaction="setup")
 ```