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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -63,13 +63,13 @@ fn target_dir() -> PathBuf {
         .unwrap_or_else(|| workspace_root().join("target"))
 }
 
-fn local_grok_binary_path() -> PathBuf {
+fn local_kigi_binary_path() -> PathBuf {
     target_dir()
         .join("debug")
         .join(format!("kigi-tui{}", std::env::consts::EXE_SUFFIX))
 }
 
-fn ensure_local_grok_binary(binary: &Path) {
+fn ensure_local_kigi_binary(binary: &Path) {
     if binary.exists() {
         return;
     }
@@ -95,8 +95,8 @@ fn ensure_local_grok_binary(binary: &Path) {
     );
 }
 
-/// Resolve grok binary: `KIGI_BINARY` env (CI) or a locally built `kigi-tui` binary.
-pub fn grok_binary() -> PathBuf {
+/// Resolve kigi binary: `KIGI_BINARY` env (CI) or a locally built `kigi-tui` binary.
+pub fn kigi_binary() -> PathBuf {
     if let Ok(path) = std::env::var("KIGI_BINARY") {
         let p = PathBuf::from(path);
         assert!(p.exists(), "KIGI_BINARY does not exist: {}", p.display());
@@ -110,8 +110,8 @@ pub fn grok_binary() -> PathBuf {
         }
     }
 
-    let binary = local_grok_binary_path();
-    ensure_local_grok_binary(&binary);
+    let binary = local_kigi_binary_path();
+    ensure_local_kigi_binary(&binary);
     binary
 }
 
@@ -149,14 +149,14 @@ pub fn git_workdir() -> TempDir {
     dir
 }
 
-/// Point grok at the mock server with a fake API key and telemetry disabled.
+/// Point kigi at the mock server with a fake API key and telemetry disabled.
 pub fn test_env_cmd_tokio(
     cmd: &mut tokio::process::Command,
     mock_url: &str,
     home: &std::path::Path,
 ) {
     cmd.env("HOME", home)
-        // HOME alone does not sandbox grok on Windows: the product resolves
+        // HOME alone does not sandbox kigi on Windows: the product resolves
         // `~` via `USERPROFILE`/Known Folders (`std::env::home_dir()`), so
         // without an explicit KIGI_SHARE_DIR every spawned child shares the real
         // `%USERPROFILE%\.kigi` — test 1's models_cache.json (which embeds