§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test could previously reach the real api.moonshot.cn), and the outdated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/tests/pty_auto_mode.rs

@@ -49,10 +49,10 @@ fn dirs_next_home() -> Option<PathBuf> {
 /// auto-permission-mode feature gate pinned explicitly via `gate_on` so each
 /// test is self-contained and deterministic regardless of the runner's shell.
 fn prepare_sandbox(home: &Path, gate_on: bool) -> Vec<(String, String)> {
-    let grok = home.join(".kigi");
-    let _ = std::fs::create_dir_all(&grok);
+    let kigi = home.join(".kigi");
+    let _ = std::fs::create_dir_all(&kigi);
     if let Some(src) = auth_json_source() {
-        let dest = grok.join("auth.json");
+        let dest = kigi.join("auth.json");
         if let Err(e) = std::fs::copy(&src, &dest) {
             eprintln!("pty_auto_mode: could not copy auth.json ({e}); login may block mode cycle");
         } else {
@@ -69,7 +69,7 @@ fn prepare_sandbox(home: &Path, gate_on: bool) -> Vec<(String, String)> {
     let home_s = home.display().to_string();
     let mut env = vec![
         ("HOME".into(), home_s.clone()),
-        ("KIGI_SHARE_DIR".into(), grok.display().to_string()),
+        ("KIGI_SHARE_DIR".into(), kigi.display().to_string()),
         ("XDG_CONFIG_HOME".into(), format!("{home_s}/.config")),
         ("XDG_DATA_HOME".into(), format!("{home_s}/.local/share")),
         ("XDG_CACHE_HOME".into(), format!("{home_s}/.cache")),