Rebrand auth guidance strings: grok login/logout -> kigi login/logout

The headless not-signed-in message still pointed at `grok login` and
XAI_API_KEY; error copy across the shell (re-auth prompts, managed-config
rejection, mcp doctor, trace classifier) and kigi-bin did too. All now
reference `kigi login` / `kigi logout`, and the headless fallback points
at the Moonshot open-platform key (KIGI_MOONSHOT_API_KEY).

crates/codegen/kigi-shell/src/managed_config.rs

@@ -98,7 +98,7 @@ pub fn clear_orphan() {
 }
 
 /// Best-effort cross-process lock serializing apply/remove of the managed-config
-/// files (TUI tick vs `grok login` vs prefetch). `None` on contention — the
+/// files (TUI tick vs `kigi login` vs prefetch). `None` on contention — the
 /// caller skips and retries next cycle.
 fn try_lock_managed_config(home: &std::path::Path) -> Option<std::fs::File> {
     use fs2::FileExt;
@@ -645,7 +645,7 @@ pub enum ManagedConfigSync {
     Failed,
 }
 
-/// Post-login hook for `grok login` and the ACP/TUI authenticate flow: clear any
+/// Post-login hook for `kigi login` and the ACP/TUI authenticate flow: clear any
 /// orphaned files, then fetch the new principal's config immediately rather than
 /// waiting for the background tick. `authenticated` pins the just-logged-in
 /// principal (`None` = on-disk team). Latency-bounded by [`SyncBudget::Login`];