Add new_tex_uwletter script (moved from ~/bin) with bug fixes: set -e,
quoted variables, WORK_DIR instead of TMPDIR, existence check for
destination, and mktemp inside the conditional. Update README to fix
stale URLs, ShareLaTeX -> Overleaf, MacOSX -> macOS, typo in
Dasgupta's email, and add script usage section.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- fully incorporated back sayamindu's stuff for dealing with encrypted
signatures files (not a bad idea!)
- removed an old uw-header file from a previous version
