fix(chat): keep messages chronological across ID rollover

packages/vscode/CHANGELOG.md

@@ -1,3 +1,7 @@
+## [Unreleased]
+
+- **Chat:** new messages now remain at the end of the conversation instead of jumping before older messages after the message ID sequence rolls over; history loading, revert, and redo follow the same chronological order.
+
 ## [1.18.3] - 2026-08-14
 
 - Chat images: completed assistant replies now collect Markdown images into a compact gallery with thumbnails and full-screen previews, including workspace-local images across multi-root workspaces (thanks to @ChangeHow).

packages/vscode/src/DOCUMENTATION.md

@@ -72,6 +72,10 @@ The webview CSP permits `blob:` only for `worker-src` so shared UI parsers can r
   - Owns the persisted VS Code permission auto-accept policy and its GET/PUT bridge contract.
   - Serializes reads and read-modify-write updates, persists a monotonic policy revision, and broadcasts the exact committed snapshot to every active OpenChamber webview. Permission replies remain foreground UI-owned because VS Code does not run the OpenChamber server runtime.
 
+## Shared webview message ordering
+
+Message and part ordering is owned by [`packages/ui/src/sync/DOCUMENTATION.md`](../../ui/src/sync/DOCUMENTATION.md#session-message-loading). The VS Code webview consumes that shared sync implementation; bridge and proxy runtimes pass OpenCode records through without adding runtime-specific ordering.
+
 ## Extension guideline
 
 When adding new bridge route families: