Brand the fork as Hellion Chat with independent plugin state

Switch the assembly name to HellionChat so Dalamud uses
pluginConfigs/HellionChat for our config file and database
directory, instead of sharing those locations with the upstream
Chat 2 plugin. Code namespace stays ChatTwo.* so upstream
cherry-picks apply cleanly.

Rename the DalamudPackager manifest to HellionChat.yaml with
fork-specific name, author, repo URL, description, tags and
changelog. Plugin.PluginName becomes "Hellion Chat".

Add a one-shot migration in the plugin constructor that runs
before GetPluginConfig: if pluginConfigs/ChatTwo.json or the
ChatTwo/ directory exist and our equivalents don't, move them
into the HellionChat layout. Idempotent: only fires on the first
load where legacy paths are present and ours are not.

ChatTwo/ChatTwo.csproj

@@ -2,6 +2,13 @@
     <PropertyGroup>
         <Version>1.35.3</Version>
         <ImplicitUsings>enable</ImplicitUsings>
+        <!-- HellionChat fork: assembly is renamed so Dalamud uses
+             pluginConfigs/HellionChat instead of pluginConfigs/ChatTwo,
+             keeping our state independent from the upstream plugin.
+             Code namespace stays ChatTwo.* so upstream cherry-picks
+             apply cleanly. -->
+        <AssemblyName>HellionChat</AssemblyName>
+        <RootNamespace>ChatTwo</RootNamespace>
     </PropertyGroup>
 
     <ItemGroup>