chore: tighten .vscodeignore to exclude dev files from VSIX

Excludes tests/, coverage/, scripts/, CLAUDE.md, DEV.md, demo-python-project/,
.github/, .claude/, jest.config.ts — cuts packaged file count from 60 to 20.

Author: kool7

.vscodeignore

@@ -5,3 +5,13 @@ src/**
 tsconfig.json
 **/*.map
 node_modules/**
+tests/**
+coverage/**
+scripts/**
+demo-python-project/**
+.github/**
+.claude/**
+CLAUDE.md
+DEV.md
+jest.config.ts
+*.vsix