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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -73,7 +73,7 @@ fn line_col(src: &str, byte: usize) -> (usize, usize) {
 }
 
 /// [`load_toml_file`] plus that layer's `[[version_overrides]]`. Use for
-/// grok config files; use [`load_toml_file`] directly for unrelated TOML.
+/// kigi config files; use [`load_toml_file`] directly for unrelated TOML.
 pub fn load_config_file(path: &Path) -> std::io::Result<toml::Value> {
     let mut v = load_toml_file(path)?;
     apply_version_overrides_with_registered(&mut v)?;
@@ -637,7 +637,7 @@ mod tests {
     fn load_user_config_layer_reads_file_when_home_present() {
         use std::io::Write;
 
-        let dir = std::env::temp_dir().join(format!("grok-load-layer-{}", std::process::id()));
+        let dir = std::env::temp_dir().join(format!("kigi-load-layer-{}", std::process::id()));
         std::fs::create_dir_all(&dir).unwrap();
         let mut f = std::fs::File::create(dir.join("config.toml")).unwrap();
         writeln!(f, "[telemetry]\nmode = \"from_file\"\n").unwrap();
@@ -651,7 +651,7 @@ mod tests {
     /// snippet, which can carry a secret and would reach a client caller.
     #[test]
     fn parse_error_keeps_kind_but_not_snippet() {
-        let dir = std::env::temp_dir().join(format!("grok-toml-leak-{}", std::process::id()));
+        let dir = std::env::temp_dir().join(format!("kigi-toml-leak-{}", std::process::id()));
         std::fs::create_dir_all(&dir).unwrap();
         let path = dir.join("bad.toml");
         // Duplicate key: the message names the key; the secret-bearing source line is only in Display.