Web and Desktop now share one command pair: start:* launches the artifacts
of a prior complete build and dev:* builds first, then launches. start:web
is new and spells out the same source launch vector as `pnpm dsh web`;
dev:web runs `pnpm run build`, the three rebuild watchers, and `dsh web` in
one terminal, with --skip-build and --no-serve for the previous two-terminal
flow. The launcher gate pins both scripts to the dsh CLI, and a root
Makefile names the same commands as make web|dev-web|desktop|dev-desktop|build.
The dev-web stage supervisor waits for stages the terminal already
interrupted, escalates only survivors, forwards SIGTERM once, and reports a
stage that exits on its own. Signal listeners are persistent because the
tsdown watchers bundle signal-exit, which re-raises a signal when it finds
no other listener.