Remove dead code scripts

Deleted 35 unused scripts:
- 12 demo scripts (manual testing/demos)
- 19 test utility scripts (debugging scripts with inline diagnostics)
- 2 duplicate utilities (extract-all-wasm.mjs, extract-onnx-wasm.mjs)
- 2 orphaned scripts (get-coverage-percentage.mjs, constants.mjs)

These scripts were never referenced in package.json and served no active purpose.

Author: jdalton