fix: use Cursor's official attribution email (#15)

Cursor now auto-appends `Co-authored-by: Cursor
<cursoragent@cursor.com>` to agent commits (enabled by default in
Settings > Agent > Attribution). We were using `noreply@cursor.com`, so
our dedup check wouldn't recognize Cursor's own trailer — resulting in
duplicate Co-authored-by lines.

This updates our email to match Cursor's.

References:
- [Cursor Git docs](https://cursor.com/docs/integrations/git)
- [Forum: co-author added without
consent](https://forum.cursor.com/t/co-author-added-without-consent-and-cant-be-turned-off/150096)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: baldawarishi

src/agent.rs

@@ -26,7 +26,7 @@ pub const KNOWN_AGENTS: &[Agent] = &[
     Agent {
         process_names: &["cursor", "cursor-agent"],
         env_vars: &[],
-        email: "Cursor <noreply@cursor.com>",
+        email: "Cursor <cursoragent@cursor.com>",
         breadcrumb_dir: None,
         breadcrumb_ext: None,
     },