§9 acceptance: grep-zero sweep — every internal x.ai/grok identifier renamed

The PRD's first acceptance gate now holds: grep -RinE '\bx\.ai\b|grok'
crates/ --include='*.rs' → 0 matches (exempt: NOTICE and third-party
license archives, README provenance, and the required 'Based on Grok
Build Open Source' attribution, now sourced from version_attribution.txt).

Wire-visible renames (both sides in this repo, changed in lockstep):
- Auth method id 'grok.com' → 'kimi-code' (AuthMethodKind::KimiCode).
- Every x.ai/* and _x.ai/* ACP ext method and meta key → kigi/* /
  _kigi/* (~200 names; grokShell → kigiShell). Session-file replay keeps
  a read-side alias for the legacy '_x.ai/session/update' method so
  existing updates.jsonl histories load; writes emit only the new name
  (both directions test-pinned).
- Agent types grok-build* → kigi* with a documented legacy-prefix alias
  at resolution time so persisted sessions keep resolving.
- ToolNamespace/BuiltinAgentName GrokBuild* → Kigi* (wire snake_case
  kigi/kigi_concise/kigi_hashline; schema regenerated); grok_build
  implementation dirs renamed to kigi*.
- x-grok-* headers → x-kigi-*, __GROK_* sentinels → __KIGI_*, themes
  grokday/groknight → kigiday/kiginight (old persisted values fall back
  to the default theme), web_fetch allowlist xAI hosts → kimi.com +
  moonshot platforms, changelog CDN → this repo, grok-build changelog
  archives deleted.
- BYOK default endpoint removed: [endpoints] api_base_url is now truly
  optional with NO default — consumers fail fast with the flag name when
  unset (no silent x.ai egress). Mock harnesses inject it explicitly.
- System-prompt identity fixed: 'released by xAI' → 'an unofficial
  community CLI for Kimi' (template + regenerated encrypted form).

Also repaired pre-existing grok-era test debt found by the sweep: the
stale trace_classify default-model pin, the grok-pager UA label test,
pty-harness stale-binary reuse and non-hermetic moonshot routing (a PTY
test could previously reach the real api.moonshot.cn), and the outdated
oauth fixture scope key.

Gates: §9 grep 0; fmt clean; workspace check/clippy 0/0 (-D warnings);
FULL cargo test --workspace: 234 suites, 21,961 passed, 0 failed;
deny advisories ok.

crates/codegen/kigi-tui/src/app/acp_handler/session_notification.rs

@@ -101,7 +101,7 @@ pub(super) fn advance_reconnect_cursor(agent: &mut AgentView, meta: &mut Notific
         agent.last_seen_event_id = Some(id);
     }
 }
-/// Handle `x.ai/session_notification` and replay-path `x.ai/session/update`.
+/// Handle `kigi/session_notification` and replay-path `kigi/session/update`.
 ///
 /// Routes by `session_id` so events for an inactive agent still mutate that
 /// agent's state. The redraw decision is gated on whether the matched agent
@@ -133,7 +133,7 @@ pub(super) fn handle_session_notification(notif: &acp::ExtNotification, app: &mu
             tracing::debug!(
                 session_id = session_notif.session_id.0.as_ref(),
                 method = notif.method.as_ref(),
-                "load-race: x.ai/session_notification DROPPED — no agent matches session_id"
+                "load-race: kigi/session_notification DROPPED — no agent matches session_id"
             );
             return false;
         }
@@ -159,7 +159,7 @@ pub(super) fn handle_session_notification(notif: &acp::ExtNotification, app: &mu
         agent,
         &meta,
         session_notif.session_id.0.as_ref(),
-        "x.ai/session/update",
+        "kigi/session/update",
     ) {
         return false;
     }
@@ -174,7 +174,7 @@ pub(super) fn handle_session_notification(notif: &acp::ExtNotification, app: &mu
             session_id = session_notif.session_id.0.as_ref(),
             event_seq = meta.event_seq,
             last_applied = agent.last_applied_xai_event_seq,
-            "x.ai/session update DROPPED by dedup highwater (event_seq <= last_applied)"
+            "kigi/session update DROPPED by dedup highwater (event_seq <= last_applied)"
         );
         return false;
     }