release(v1.5.4): manifest bump and forge post

Bumps csproj, yaml, repo.json, CHANGELOG, ROADMAP and README in
lock-step to 1.5.4. Forge-post DE-body added with the Polish & Motion
versionsnatur. Slim-rule applied to the yaml and repo.json changelog
blocks (keeps v1.5.4 + v1.5.3 + v1.5.2 + v1.5.1, drops v1.5.0).

A csharpier reflow of two v1.5.4 source files (ChatLogWindow,
HellionStyle) is folded in. preflight.sh blocks A-F all green.

HellionChat/Ui/HellionStyle.cs

@@ -49,10 +49,7 @@ internal static class HellionStyle
         // per-window opacity override and must not fade. See
         // feedback_dalamud_pinning_override.
         ThemeAbgrCache a;
-        if (
-            !Plugin.Config.ReduceMotion
-            && registry.TryGetActiveCrossfade(out var lerped)
-        )
+        if (!Plugin.Config.ReduceMotion && registry.TryGetActiveCrossfade(out var lerped))
         {
             a = lerped;
         }