Two changes in one file:
- Q2 mechanical: change the spawn_reaper_thread closure
signature from `Fn(u32)` to `Fn(u32, i32)`; capture
`waitpid` status via `&mut status`; pass both `res` and
`status` to the reaper callback. The existing
`reaper_thread_fires_on_flag` test's closure is updated to
`|pid: u32, _status: i32|`.
- Bug5: `run_watchdog` no longer silently `return;`s on a
reaper thread panic. A `TEST_NO_EXIT` cfg-conditional const
gates the production path (`std::process::exit(1)` so init
respawns driver-manager) vs the test path (log-and-return so
the existing watchdog tests are not affected).
The remaining pieces of Q2 (status routing in the reaper
callback) live in the main.rs Q1+Q2+S3 commit.
vasilito
a30db01cba