fix(s040): the hot-reload test waits past the mtime second (the polling backend on the gate's runners); TRINITY_SKILLS_POLL=1 forces the poll

Run 35623752961: gate and fips have no inotifywait, the registry polls once a second, and
the poll compares mtimes at one-second resolution, so an edit inside the file's first second
was no change. Under the forced poll on this machine the edit arrives in about 1.2 s.

Signed-off-by: Ayla Croft <aylacroft@proton.me>

Author: HackTuah

lib/trinity/skills/registry.ex

@@ -301,22 +301,27 @@ defmodule Trinity.Skills.Registry do
   end
 
   # inotify needs the `inotifywait` executable; without it, and on any platform file_system
-  # has no native backend for, poll once a second (AC3's 2 s still holds).
+  # has no native backend for, poll once a second (AC3's 2 s still holds; the poll compares
+  # mtimes at one-second resolution). `TRINITY_SKILLS_POLL=1` forces the poll, so the
+  # fallback can be exercised on a machine that has inotifywait.
   defp backend do
-    case :os.type() do
-      {:unix, :linux} ->
-        if System.find_executable("inotifywait"),
-          do: [],
-          else: [backend: :fs_poll, interval: 1_000]
+    poll = [backend: :fs_poll, interval: 1_000]
 
-      {:unix, :darwin} ->
+    cond do
+      System.get_env("TRINITY_SKILLS_POLL") == "1" ->
+        poll
+
+      match?({:unix, :linux}, :os.type()) ->
+        if System.find_executable("inotifywait"), do: [], else: poll
+
+      match?({:unix, :darwin}, :os.type()) ->
         []
 
-      {:win32, _} ->
+      match?({:win32, _}, :os.type()) ->
         []
 
-      _ ->
-        [backend: :fs_poll, interval: 1_000]
+      true ->
+        poll
     end
   end
 

slices/040-skills-registry/proof/ac7-1-skills.png

@@ -123,8 +123,11 @@ defmodule Trinity.Skills.RegistryTest do
     Registry.rescan()
     assert Skills.get("watched").description == "Before."
     # inotifywait establishes its watches a moment after it starts and says nothing when it
-    # has; an edit before that is missed (one run in three without this pause).
-    Process.sleep(500)
+    # has; an edit before that is missed (one run in three without a pause). And the polling
+    # backend the registry picks where inotifywait is absent (the gate's runners, run
+    # 35623752961) compares mtimes at one-second resolution: an edit inside the second the
+    # file was written in is no change to it. So the edit waits a second and a bit.
+    Process.sleep(1_100)
 
     File.write!(
       Path.join([dir, "watched", "SKILL.md"]),