chore: bump version to 1.4.9, sync manifest

Manifest version bump for the v1.4.9 release cut. Schema-required v16
stays unchanged (R1/R2/R3 are all config-neutral refactors).

Files touched:
- HellionChat/HellionChat.csproj: <Version> 1.4.8 -> 1.4.9
- HellionChat/Plugin.cs: schema-migration error string self-reference
  (v1.4.8 -> v1.4.9, required schema v16 stays)
- repo.json: AssemblyVersion, TestingAssemblyVersion, 3x DownloadLink*
  URLs all bumped to 1.4.9 / v1.4.9. Changelog field is still on v1.4.8;
  the v1.4.9 block plus v1.4.5 slim-drop land in the next commit.
- README.md: shield badge, version header in lead paragraph, project-
  status block rewritten for v1.4.9 (Plugin-Load Render Polish).
- docs/CHANGELOG.md: v1.4.9 block inserted above v1.4.8.
- docs/ROADMAP.md: v1.4.9 moved into the released-versions list,
  "Next Cycle" header now targets v1.4.10 (Render Clipper + Symbol
  Picker reserves carried over from the v1.4.9 plan).

yaml changelog block and repo.json Changelog field follow in the
docs commit so the slim-drop of v1.4.5 stays atomic with the v1.4.9
block insert.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

HellionChat/Plugin.cs

@@ -189,8 +189,8 @@ public sealed class Plugin : IAsyncDalamudPlugin
         if (Config.Version < 16)
         {
             throw new InvalidOperationException(
-                $"HellionChat v1.4.8 requires config schema v16, got v{Config.Version}. "
-                    + "Please install v1.4.2 first to migrate the configuration, then upgrade to v1.4.8."
+                $"HellionChat v1.4.9 requires config schema v16, got v{Config.Version}. "
+                    + "Please install v1.4.2 first to migrate the configuration, then upgrade to v1.4.9."
             );
         }
         Config.Version = 17;