macOS bundle: eliminate fork() — thread decode pool (NEXRAD_INPROC_POOL) + open browser via os.posix_spawn (Obj-C process aborts on fork)

Briefcase launcher: open browser via macOS /usr/bin/open (robust) + keep-alive marker

Briefcase: open app in default browser instead of pywebview (pyobjc segfaults in the thinned bundle); force fork for the decode pool; drop pywebview/pyobjc/proxy_tools

Briefcase: fix pywebview backtracking to 3.4 — ship proxy_tools wheel + --find-links, pin pywebview>=5, drop std-nslog (<private> log redaction)

Briefcase launcher: fix macOS-spawn worker imports (HERE on sys.path at import) + verbose startup logging + browser fallback if pywebview fails

Pin gradio==5.34.2 to match HF Space sdk_version (Space + Mac identical; avoids pip drift past sdk_version)

Pin gradio>=5,<6: app UI targets Gradio 5 (Gradio 6 dropped launch(show_api=...))

Student guide: state macOS Sonoma (14) or later as the requirement

Briefcase: min_os_version=14.0 for numpy-2-coherent stack (netCDF4 1.7.x arm64 wheel is macosx_14); add std-nslog; student install guide

Briefcase: min_os_version=12.0 (scipy/netCDF4 wheels need macOS 12+); document adhoc-sign distribution caveat

Briefcase: hyphenate app name (nexrad-l2) so module maps to src/nexrad_l2 package

Briefcase: PEP 639 SPDX license string (fixes 'briefcase create' license error)

Desktop: add Briefcase (BeeWare) build as an alternative to py2app

Desktop: free unsigned .app/.dmg build (Apple Silicon) — build_app.sh, icon, FIRST_OPEN instructions

Desktop: inherit deps from root requirements (single source); launcher interface check + sync docs

Guard background daemons under start_background() for macOS spawn-safety; add desktop launcher (pywebview)