chore(release): close the v1.13.0 cycle

Version to 1.13.0 in the csproj, with the changelog and roadmap entries for the
local state. Not published: the public release stays at v1.5.6, repo.json keeps
its 1.5.6.0 manifest and all three download links are untouched.

The changelog leads with the screenshot-mode gap rather than with the typography,
because that is the part that changes what a user's own screenshots contain. An
auto-tell tab is named "Player@World", and three of the four surfaces that draw a
tab name had no rule about it -- so a picture of the default view named the
conversation partner while every message below it was anonymised. Anyone who has
shared a screenshot from an older build should know that.

Config version 26 is in there for the same reason. Its migration marks existing
tell tabs as partner-named, and it says plainly what it cannot do: a tab promoted
to permanent before this version keeps its name and loses every marker, so
nothing in the stored data says where that name came from.

Known issues carry the honest tail: the header recomputes its widths every frame
instead of on the status bar's tick, and all three font handles now rasterise the
full glyph range -- the cost of letting the channel name use the smaller face
without breaking on an umlaut.

The migration self-test asserts what v26 actually does now, rather than only that
the version number moved.

HellionChat/HellionChat.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Dalamud.NET.Sdk/15.0.0">
     <PropertyGroup>
         <!-- Independent versioning; see yaml changelog for upstream Chat 2 base -->
-        <Version>1.12.0</Version>
+        <Version>1.13.0</Version>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <!-- Use lock file to pin exact versions -->

HellionChat/SelfTests/ConfigMigrationV26Step.cs

@@ -25,6 +25,23 @@ internal sealed class ConfigMigrationV26Step : ISelfTestStep
             return SelfTestStepResult.Fail;
         }
 
+        // What v26 exists to prevent: a tab whose name came from a conversation
+        // partner but is not marked as such, because screenshot mode reads that
+        // mark to decide whether the name may be shown. Anything still holding a
+        // tell binding or the temp flag should have been marked on load.
+        foreach (var tab in Plugin.Config.Tabs)
+        {
+            var looksLikeAPartner = tab.IsTempTab || tab.TellTarget?.IsSet() == true;
+            if (!looksLikeAPartner || tab.NameCameFromPartner)
+                continue;
+
+            ImGui.Text(
+                $"Tab '{tab.Name}' carries a tell binding but is not marked partner-named "
+                    + "— the v26 migration did not reach it, and screenshot mode will show it"
+            );
+            return SelfTestStepResult.Fail;
+        }
+
         // The state the v24 migration exists to prevent: filter on, failsafe on,
         // nothing picked. Under the corrected rule that combination stores no
         // messages at all, so reaching /xlperf in it means the migration did not