§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test could previously reach the real api.moonshot.cn), and the outdated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-shell/src/session/goal_orchestrator.rs

@@ -104,7 +104,7 @@ impl GoalNotifySender {
         }
         if let Some(raw) = raw {
             let ext = agent_client_protocol::ExtNotification::new(
-                "x.ai/session_notification",
+                "kigi/session_notification",
                 raw.into(),
             );
             self.gateway.forward_fire_and_forget(ext);
@@ -432,7 +432,7 @@ mod tests {
         // — the wire field stays empty so the doc contract holds and we
         // don't ship a 1-element vec the pager would collapse anyway.
         let mut o = make_base_orchestration();
-        o.live_tokens_by_model = vec![("grok-4".into(), 5_000)];
+        o.live_tokens_by_model = vec![("kigi-4".into(), 5_000)];
         match build_goal_updated(&o, 0, 0) {
             XaiSessionUpdate::GoalUpdated {
                 live_tokens_by_model,
@@ -445,14 +445,14 @@ mod tests {
         }
 
         // ≥2 distinct models are transmitted verbatim.
-        o.live_tokens_by_model = vec![("grok-4".into(), 5_000), ("grok-3".into(), 3_000)];
+        o.live_tokens_by_model = vec![("kigi-4".into(), 5_000), ("kigi-3".into(), 3_000)];
         match build_goal_updated(&o, 0, 0) {
             XaiSessionUpdate::GoalUpdated {
                 live_tokens_by_model,
                 ..
             } => assert_eq!(
                 live_tokens_by_model,
-                vec![("grok-4".to_owned(), 5_000), ("grok-3".to_owned(), 3_000)]
+                vec![("kigi-4".to_owned(), 5_000), ("kigi-3".to_owned(), 3_000)]
             ),
             _ => panic!("expected GoalUpdated"),
         }