§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test could previously reach the real api.moonshot.cn), and the outdated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-shell/src/sampling/error.rs

@@ -2,7 +2,7 @@
 //!
 //! The canonical error types now live in `kigi_sampling_types::error`.
 //! This module re-exports them and adds `map_sampling_err_to_acp` which
-//! depends on `agent_client_protocol::Error` (a grok-shell dependency).
+//! depends on `agent_client_protocol::Error` (a kigi-shell dependency).
 
 // Re-export everything from the standalone crate.
 pub use kigi_sampling_types::error::*;
@@ -72,7 +72,7 @@ pub fn map_sampling_err_to_acp(err: SamplingError) -> acp::Error {
             // explanation visible to the user without triggering the client's
             // re-auth flow on -32000.
             StatusCode::FORBIDDEN => {
-                let message = if message.contains("requires a Grok subscription")
+                let message = if message.contains("requires a Kigi subscription")
                     && crate::agent::auth_method::has_xai_api_key_env()
                 {
                     format!(
@@ -477,7 +477,7 @@ mod tests {
         with_api_key_env(Some("xai-test"), || {
             let err = SamplingError::Api {
                 status: StatusCode::FORBIDDEN,
-                message: "The model 'grok-build' requires a Grok subscription.".into(),
+                message: "The model 'kigi' requires a Kigi subscription.".into(),
                 model_metadata: None,
                 retry_after_secs: None,
             };
@@ -501,7 +501,7 @@ mod tests {
         with_api_key_env(None, || {
             let err = SamplingError::Api {
                 status: StatusCode::FORBIDDEN,
-                message: "The model 'grok-build' requires a Grok subscription.".into(),
+                message: "The model 'kigi' requires a Kigi subscription.".into(),
                 model_metadata: None,
                 retry_after_secs: None,
             };