§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test could previously reach the real api.moonshot.cn), and the outdated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-pager-pty-harness/src/leader.rs

@@ -38,7 +38,7 @@ impl LeaderCluster {
         // One shared KIGI_SHARE_DIR => one leader; the socket lives beneath it so
         // every client (sharing the same env) elects/attaches to the same one.
         let kigi_home = content.home().join(".kigi");
-        std::fs::create_dir_all(&kigi_home).context("create grok home")?;
+        std::fs::create_dir_all(&kigi_home).context("create kigi home")?;
         let socket = kigi_home.join("leader-e2e.sock");
         let binary = pager_binary().context("resolve pager binary")?;
         Ok(Self {
@@ -194,14 +194,14 @@ mod tests {
     /// Wrap a session update as the envelope stored in `updates.jsonl`.
     fn envelope(update_json: &str) -> String {
         format!(
-            r#"{{"timestamp":1,"method":"_x.ai/session/update","params":{{"sessionId":"s","update":{update_json}}}}}"#
+            r#"{{"timestamp":1,"method":"_kigi/session/update","params":{{"sessionId":"s","update":{update_json}}}}}"#
         )
     }
 
     #[test]
     fn parse_update_payloads_unwraps_and_tolerates_torn_trailing_line() {
         let body = format!(
-            "{}\n{}\n{{\"timestamp\":2,\"method\":\"_x.ai/sess",
+            "{}\n{}\n{{\"timestamp\":2,\"method\":\"_kigi/sess",
             envelope(
                 r#"{"sessionUpdate":"agent_message_chunk","content":{"type":"text","text":"hi"}}"#
             ),