chore(release): v1.5.1 manifest bump

- csproj <Version> 1.5.0 to 1.5.1; <None Include="images\**"> now
  excludes the source-only ASCII study folder so the deploy stays
  clean
- yaml + repo.json changelog block prepended with the v1.5.1 entry,
  v1.4.8 trimmed out per the slim rule (three to four versions in
  the manifest cache, older history lives on the Gitea release page)
- repo.json AssemblyVersion + TestingAssemblyVersion bumped to
  1.5.1.0, three DownloadLink* URLs point at v1.5.1
- docs/CHANGELOG and docs/ROADMAP gain the v1.5.1 entry; ROADMAP
  Next-Cycle slot moves to v1.5.2 First-Run-Wizard rework
- README status sections updated, the previous v1.5.0 paragraph
  kept under a "Project status (pre-v1.5.1, kept for context)"
  heading
- Forge-post .github/forge-posts/v1.5.1.md added, DE body honest
  about the HITCH-win miss
- yamllint config ignores the plugin manifest yaml because it
  follows DalamudPackager's 4-space indent convention rather than
  yamllint's default 2

Changelogs are honest about the cross-plugin HITCH target from
v1.5.0 not landing this cycle.

docs/CHANGELOG.md

@@ -11,6 +11,38 @@ releases as an overview and links to the release pages for details.
 
 ---
 
+## Hellion Chat 1.5.1 — FontAtlas Refactor and Hellion Forge Signature (2026-05-17)
+
+Hybrid FontManager refactor plus an embedded Hellion Forge provenance mark.
+
+- FontManager handle creation moves into the ctor inside a single `atlas.SuppressAutoRebuild()`
+  block — the font atlas now builds once per plugin load instead of four to five times.
+- Hybrid property model: `Axis`, `AxisItalic` and `FontAwesome` become init-only handles;
+  `RegularFont` and `ItalicFont` stay mutable because the eight font settings still need to replace
+  them at runtime via the renamed `RebuildDelegateFonts()` path, without a plugin reload.
+- `FontAwesome` reuses Dalamud's `UiBuilder.IconFontFixedWidthHandle` instead of building its own
+  atlas slot.
+- `BuildFontsAsync` and `BuildFonts` are removed; the live mutation path is `RebuildDelegateFonts()`
+  now.
+- Two new self-test steps register with `/xlperf`: FontManager ctor smoke (every handle non-null, no
+  atlas load-exception) and push smoke (`Push()` returns without throwing).
+- Hellion Forge signature embedded in the plugin DLL: a fox-head ASCII silhouette is prepended to
+  the `/xllog` bootstrap banner on every plugin load, and a full fox banner with "Hellion Forge" set
+  inside the body is available as a folded `TreeNode` in the First-Run Wizard and Settings →
+  Information tab. Drawn by Julia Moon.
+- Honorific full-gradient port (originally scheduled for this cycle) was dropped: Honorific 3.2
+  exposes no IPC for the rendered gradient frame, and an in-plugin port of the colour palette was
+  declined. The integration stays at the v1.4.7 glow-only shape.
+
+The 10× HITCH cut targeted from the v1.5.0 cross-plugin baseline did not land — HITCH stays around
+80 ms because the cost lives in the UiBuilder first-frame render path, not in the atlas build (which
+this cycle did reduce from 4-5 builds per load to 1). A first-frame render investigation is reserved
+for a later cycle. No settings changes, no migration. v17 stays.
+
+[Full release notes on the Gitea release page.](https://gitea.hellion-forge.cloud/JonKazama-Hellion/HellionChat/releases/tag/v1.5.1)
+
+---
+
 ## Hellion Chat 1.5.0 — DI Foundation and Service Refactor (2026-05-17)
 
 Major architecture cycle. The plugin bootstrap moves to a generic-host DI container