§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test could previously reach the real api.moonshot.cn), and the outdated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/util/config/mcp.rs

@@ -1329,7 +1329,7 @@ auto_update = true
         // Test with no cli section at all
         let toml_str = r#"
 [models]
-default = "grok-code-fast-1"
+default = "kigi-code-fast-1"
 "#;
         let root: TomlValue = toml::from_str(toml_str).unwrap();
         if let TomlValue::Table(ref table) = root {
@@ -1374,7 +1374,7 @@ auto_update = true
     fn test_use_leader_opt_returns_none_when_no_cli_section() {
         let toml_str = r#"
 [models]
-default = "grok-code-fast-1"
+default = "kigi-code-fast-1"
 "#;
         let root: TomlValue = toml::from_str(toml_str).unwrap();
         assert_eq!(use_leader_from_toml_opt(&root), None);
@@ -1702,10 +1702,10 @@ expose_image_base64 = true
     #[test]
     fn mcp_json_all_toml_names_includes_disabled() {
         let tmp = tempfile::tempdir().unwrap();
-        let grok_dir = tmp.path().join(".kigi");
-        std::fs::create_dir_all(&grok_dir).unwrap();
+        let kigi_dir = tmp.path().join(".kigi");
+        std::fs::create_dir_all(&kigi_dir).unwrap();
         std::fs::write(
-            grok_dir.join("config.toml"),
+            kigi_dir.join("config.toml"),
             r#"
 [mcp_servers.enabled_one]
 url = "https://example.com"