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.

docs/ROADMAP.md

@@ -22,6 +22,18 @@ parallel as a continuous correction pass, gathered via the Hellion Forge Discord
 
 ---
 
+## v1.5.4 — Polish and Motion (released 2026-05-20)
+
+A polish cycle of three P3 items. Theme switches crossfade over ~300 ms across every
+Hellion-rendered surface; the window background snaps deliberately to preserve the
+per-window opacity override from Dalamud's pinning menu. A header quick-picker — a
+palette button left of the cog — switches themes and tabs from a compact popup without
+opening Settings. Sidebar icons and card-mode borders gain framerate-independent hover
+animations. A new "Reduce motion" toggle in Theme & Layout covers accessibility. No
+schema bump; migration v17 stays.
+
+---
+
 ## v1.5.3 — Localisation Wave + Bundled-Font Overhaul (released 2026-05-19)
 
 Twenty-four selectable UI languages: from FR-only as the original plan scope, the cycle expanded to