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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -42,7 +42,7 @@ pub(crate) fn find_mcp_json_files_in(chain_dirs: &[PathBuf]) -> Vec<PathBuf> {
 }
 
 /// True when `config_path` is `$KIGI_SHARE_DIR/config.toml` (user tier, not project).
-fn is_user_grok_config_file(config_path: &Path) -> bool {
+fn is_user_kigi_config_file(config_path: &Path) -> bool {
     let Some(user_home) = kigi_config::user_kigi_home() else {
         return false;
     };
@@ -79,7 +79,7 @@ pub(crate) fn find_project_configs_in(chain_dirs: &[PathBuf]) -> Vec<PathBuf> {
         .iter()
         .rev()
         .map(|dir| dir.join(".kigi").join("config.toml"))
-        .filter(|config_path| config_path.is_file() && !is_user_grok_config_file(config_path))
+        .filter(|config_path| config_path.is_file() && !is_user_kigi_config_file(config_path))
         .collect()
 }
 
@@ -88,7 +88,7 @@ mod tests {
     use super::*;
 
     #[test]
-    fn find_project_configs_excludes_user_grok_config_file() {
+    fn find_project_configs_excludes_user_kigi_config_file() {
         let Some(user_home) = kigi_config::user_kigi_home() else {
             return;
         };
@@ -98,10 +98,10 @@ mod tests {
             let home = std::env::home_dir().expect("home dir");
             let from_home = find_project_configs(&home);
             assert!(
-                !from_home.iter().any(|p| is_user_grok_config_file(p)),
+                !from_home.iter().any(|p| is_user_kigi_config_file(p)),
                 "user config leaked into project configs: {from_home:?}"
             );
-            assert!(is_user_grok_config_file(&user_config));
+            assert!(is_user_kigi_config_file(&user_config));
         }
 
         let tmp = tempfile::tempdir().unwrap();
@@ -110,6 +110,6 @@ mod tests {
         std::fs::write(project.join(".kigi/config.toml"), "# project\n").unwrap();
         let found = find_project_configs(&project);
         assert_eq!(found.len(), 1);
-        assert!(!is_user_grok_config_file(&found[0]));
+        assert!(!is_user_kigi_config_file(&found[0]));
     }
 }