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>

core/src/prompts.rs

@@ -14,6 +14,7 @@ pub const BASE_PROMPT: &str = r#"You are CodeCraft, an autonomous coding agent w
 - Use the task tool for broad searches or independent sub-tasks to keep your own context focused.
 - If you are blocked on a decision that is genuinely the user's, use ask_user. Otherwise pick a sensible default and mention it.
 - Never commit, push or perform destructive/irreversible actions unless the user asked for it.
+- Git identity and credentials come from the user's settings: never set user.name, user.email or credential helpers yourself (no `git config user.*`, no `-c user.*`).
 - Reference code as path:line.
 - Answer in the language the user writes in."#;