Git identity from the settings for all agent shells, terminals and the git panel

Set GIT_AUTHOR_*/GIT_COMMITTER_* from Settings → Account → Git (also inside the
sandbox), so a repository's own user.name/user.email no longer wins; tell agents
not to change the git identity.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/whatsnew.ts

@@ -3,6 +3,10 @@
  * under "unreleased"; scripts/release.sh renames the key to the release version.
  */
 export const WHATS_NEW: Record<string, { en: string[]; de: string[] }> = {
+  unreleased: {
+    en: ["Agents commit with the git name and e-mail from your settings – also in repositories with their own identity"],
+    de: ["Agents committen mit Git-Name und -E-Mail aus deinen Einstellungen – auch in Repos mit eigener Identität"],
+  },
   "202611-00004": {
     en: [
       "Chats side by side: “Open beside” in a chat's menu in the sidebar",