Let somebody extend this without forking it, and say when things die

Two of Section F.

Hooks are the pressure valve. "Can Panama also do X when the theme
changes" is now a five-line file in ~/.config/panama/hooks rather than
a fork, a feature request, or a patch somebody rebases forever. Each
name takes a single file and a .d directory so several things can react
without fighting over one, and a broken hook is reported and stepped
over: somebody's script must never cost a theme change, an upgrade or a
login. Wired at theme-set, post-upgrade and post-migrate. This is the
thirty-line version of the plugin host the upstream ledger defers, and
it has no API to keep stable beyond "we will run your script and tell
you what happened".

Testing it caught a real bug the reading would not have: run_one
captured the script path but never shifted it off, so every hook got
its own filename as $1 and the real arguments arrived one place late. A
hook reading $1 as the colour scheme got a path.

The crash watcher notices when a program dumps core and says so. Under
GNOME, ABRT does this; here nothing did, and applications died silently,
which is most of how "Linux is flaky" gets earned.

Once per program per session is the entire design, not a nicety. This
machine's portal backend crashes between eleven and sixty times a day,
and a notification per crash would be one every few minutes for
something nobody can act on. The first is news; the fortieth is why
people turn notifications off. The health page keeps the running count.

It waits for the notification server before reporting, because the
crash most worth hearing about is the one that took the shell with it,
and it names the executable rather than the kernel's comm field, which
truncates at fifteen characters. Verified against real segfaults.

config/dot/panama/hooks/theme-set.sample

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+# Runs whenever the colour scheme or accent changes.
+#
+#   $1  scheme: "dark" or "light"
+#   $2  accent: blue, orchid, teal, green, amber, orange, rose or slate
+#
+# Copy to ~/.config/panama/hooks/theme-set and make it executable. Anything in
+# theme-set.d/ runs too, in sorted order, so several things can react without
+# fighting over one file.
+#
+# A failure here is reported and stepped over: it will never cost you a theme
+# change.
+
+scheme="$1"
+accent="$2"
+
+# For example: repaint something Panama does not know about.
+# printf 'set-theme %s\n' "$scheme" | nc -U "$HOME/.local/share/some-app/socket"