build: configure npm package for publication

Phase 4-5 Complete:
- ✅ Updated package.json to v1.0.0 with proper entry points
- ✅ Added peer dependency on marked.js (^11.0.0 || ^12.0.0 || ^13.0.0)
- ✅ Set module type to ESM to fix Rollup warnings
- ✅ Configured files array for distribution (dist/ only)
- ✅ Added prepublishOnly script (build + test)
- ✅ Created .npmignore to exclude dev files
- ✅ Created CHANGELOG.md following Keep a Changelog format

Package details:
- Main: dist/testdrive-jsui.cjs.js (CommonJS)
- Module: dist/testdrive-jsui.esm.js (ES Module)
- Browser: dist/testdrive-jsui.min.js (107KB minified)
- Style: dist/testdrive-jsui.css
- Total package size: 445.9 KB (13 files)

npm pack --dry-run verified successfully!

.npmignore

@@ -0,0 +1,58 @@
+# Development files
+js/tests/
+tests/
+examples/
+docs/
+node_modules/
+coverage/
+.nyc_output/
+
+# Source files (we ship dist/ only)
+js/
+src/
+static/
+
+# Build config
+rollup.config.js
+.eslintrc
+.babelrc
+jest.config.js
+tsconfig.json
+
+# Documentation (except README, LICENSE, CHANGELOG)
+CLAUDE.md
+MIGRATION_STATUS.md
+CLEANUP_REPORT.md
+STANDALONE_PLAN.md
+NPM_PUBLICATION_PLAN.md
+TODO.md
+Makefile
+pyproject.toml
+
+# Python stuff
+__pycache__/
+*.py[cod]
+*.egg-info/
+venv/
+.pytest_cache/
+src/testdrive_jsui/
+
+# VCS
+.git/
+.gitignore
+.gitattributes
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Misc
+*.log
+.env