Show what a run is doing, and record when one is cut short

A run that held back a blocker then upgraded 214 packages printed one line and
then nothing for nearly five minutes while pacman downloaded and installed. It
looked hung, so it got killed - during pacman's uninterruptible commit phase,
which meant the packages landed but our bookkeeping never did. The menu then
kept showing a failure from a previous run on a fully up-to-date machine.

pacman, the AUR helper and flatpak now stream their output when a person is
watching, and the progress bar is left enabled for that case. Timer runs are
unchanged: quiet, --noprogressbar, everything captured in the log.

Interactivity is decided once at startup rather than tested at the point of
use. cau_pacman_flags runs inside a process substitution, so its stdout is
always a pipe and a -t 1 check there would have silently always been false.

INT/TERM/HUP now record last_result=interrupted, so a run that is stopped says
so instead of leaving the previous verdict standing.

src/cachy-auto-update-run

@@ -63,6 +63,21 @@ fi
 cau_config_load
 cau_log_open
 
+# Record an interruption rather than leaving the previous run's verdict behind.
+# Without this, killing an interactive run leaves last_result at whatever it was
+# before - so the menu can keep reporting a problem from hours ago while the
+# machine is in fact fully up to date, which is worse than saying nothing.
+# pacman makes the commit phase itself uninterruptible, so the packages either
+# all landed or none did; only our own bookkeeping is at risk here.
+_cau_interrupted() {
+	cau_error "Update run interrupted ($1)"
+	cau_state_write last_result interrupted
+	exit 130
+}
+trap '_cau_interrupted SIGINT'  INT
+trap '_cau_interrupted SIGTERM' TERM
+trap '_cau_interrupted SIGHUP'  HUP
+
 # ---------------------------------------------------------------------------
 # Should this run happen at all?
 # ---------------------------------------------------------------------------