chore: code quality sweep 2026-05-04 / 2026-05-05

General code-quality and robustness pass across the plugin: thread-
safety on IPC state, resource-disposal cleanups, input validation,
defensive null-checks and a few small UX glitches. Compliance docs
(THIRD_PARTY_NOTICES, PRIVACY, COPYRIGHT) refreshed to v1.0.3.

Highlights
- ExtraChat IPC state synchronised across threads
- ChatLogWindow autocomplete no longer leaks the unmanaged
  ImGuiListClipper allocation
- ChatLogWindow + Popout style stack stays balanced when config
  toggles mid-frame
- Retention sweep and privacy cleanup wait for the actual filter
  pass instead of the fire-and-forget Task that started it
- Configuration.LatestVersion bumped to 13 to match the active
  migration path
- GameFunctions placeholder buffer guarded against oversized
  replacement names
- TellTarget.IsSet, ResolveTempInputChannel, InputPreview, IconUtil,
  Lender, Payloads, ExtraPayload all hardened against null / empty /
  EOF / cycle inputs
- FontManager Lodestone download stays in scope for a follow-up
  (timeout + lazy init pending)
- AutoTranslate replaced the msvcrt.dll memcmp P/Invoke with a
  managed Span comparison
- Privacy cleanup worker thread marked IsBackground = true
- Database cleanup now removes both legacy files in one click
- Tell-target name redacted in the verbose debug log

Compliance
- THIRD_PARTY_NOTICES: last-reviewed bumped to v1.0.3, Pidgin 3.5.1,
  SQLitePCLRaw.lib.e_sqlite3 3.50.3 listed as direct dependency with
  CVE-2025-6965 / CVE-2025-7709 rationale
- PRIVACY: last-reviewed bumped to v1.0.3, BetterTTV trigger wording
  clarified (list fetch at startup vs. on-demand image fetch)
- COPYRIGHT: upstream attribution range widened

Build: 0 warnings, 0 errors. No behavioural changes that would alter
existing user configuration or stored chat history.

HellionChat/Ui/InputPreview.cs

@@ -177,7 +177,10 @@ public partial class InputPreview : Window
                 return;
 
             NextChunkIsAutoTranslate = true;
-            var payload = (AutoTranslatePayload) chunk.Link!;
+            // Malformed chunks could carry an AutoTranslateBegin icon without the matching
+            // payload; bail out instead of dereferencing a null Link.
+            if (chunk.Link is not AutoTranslatePayload payload)
+                return;
             CursorPosition += $"<at:{payload.Group},{payload.Key}>".Length;
 
             return;