§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test could previously reach the real api.moonshot.cn), and the outdated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-render/src/util.rs

@@ -11,7 +11,7 @@ pub fn pager_toml_path() -> PathBuf {
     kigi_home().join("pager.toml")
 }
 
-/// User-facing label for the user grok directory (``~/.kigi`` or ``$KIGI_SHARE_DIR``).
+/// User-facing label for the user kigi directory (``~/.kigi`` or ``$KIGI_SHARE_DIR``).
 ///
 /// Derived from resolved [`kigi_home()`] vs `kigi_config::default_kigi_home()`,
 /// not from whether `KIGI_SHARE_DIR` is set in the environment.
@@ -24,7 +24,7 @@ pub fn display_kigi_home_prefix() -> String {
 }
 
 /// User-facing path under [`kigi_home()`], e.g. ``~/.kigi/config.toml``.
-pub fn display_user_grok_path(relative: impl AsRef<Path>) -> String {
+pub fn display_user_kigi_path(relative: impl AsRef<Path>) -> String {
     let rel = relative.as_ref();
     let prefix = display_kigi_home_prefix();
     if rel.as_os_str().is_empty() {
@@ -36,8 +36,8 @@ pub fn display_user_grok_path(relative: impl AsRef<Path>) -> String {
 /// Abbreviate an absolute path for display: prefer [`kigi_home()`], then `$HOME`.
 pub fn abbreviate_path(path: &str) -> Cow<'_, str> {
     let path_buf = Path::new(path);
-    let grok = kigi_home();
-    if let Ok(rest) = path_buf.strip_prefix(&grok) {
+    let kigi = kigi_home();
+    if let Ok(rest) = path_buf.strip_prefix(&kigi) {
         let prefix = display_kigi_home_prefix();
         if rest.as_os_str().is_empty() {
             return Cow::Owned(prefix);
@@ -404,14 +404,14 @@ mod tests {
     }
 
     #[test]
-    fn display_user_grok_path_joins_relative() {
-        let path = display_user_grok_path("config.toml");
+    fn display_user_kigi_path_joins_relative() {
+        let path = display_user_kigi_path("config.toml");
         assert!(path.ends_with("/config.toml") || path.ends_with("\\config.toml"));
         assert!(path.contains(".kigi") || path.contains("$KIGI_SHARE_DIR"));
     }
 
     #[test]
-    fn abbreviate_path_uses_home_when_under_default_grok() {
+    fn abbreviate_path_uses_home_when_under_default_kigi() {
         if let Ok(home) = std::env::var("HOME") {
             if home.is_empty() {
                 return;