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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -105,7 +105,7 @@ impl ToolBridge {
     /// rather than by namespaced id.
     ///
     /// Example: `tool_for_kind(ToolKind::BackgroundTaskAction)` returns
-    /// `Some("get_task_output")` for the grok_build agent and `None` for
+    /// `Some("get_task_output")` for the kigi agent and `None` for
     /// agents that do not register a tool of that kind.
     pub async fn tool_for_kind(&self, kind: ToolKind) -> Option<String> {
         self.registry
@@ -547,9 +547,7 @@ impl ToolBridge {
         &self,
         task_id: &str,
     ) -> Result<bool, kigi_tool_runtime::ToolError> {
-        use crate::implementations::grok_build::scheduler::types::{
-            SchedulerCommand, SchedulerHandle,
-        };
+        use crate::implementations::kigi::scheduler::types::{SchedulerCommand, SchedulerHandle};
         let sender = {
             let res = self.registry.resources.lock().await;
             res.get::<SchedulerHandle>()
@@ -705,7 +703,7 @@ mod tests {
         let bridge = ToolBridge::for_test();
         let toolset = bridge.toolset();
 
-        // PascalCase + grok_build's snake_case in one registry
+        // PascalCase + kigi's snake_case in one registry
         // to exercise the lookup on the literal name strings each
         // namespace ships.
         register_fixture(&toolset, "Write", ToolKind::Write, "fixture_write");