§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test could previously reach the real api.moonshot.cn), and the outdated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/extensions/auth.rs

@@ -1,4 +1,4 @@
-//! `x.ai/auth/*` and legacy `x.ai/{get,set}ApiKey` extension handlers.
+//! `kigi/auth/*` and legacy `kigi/{get,set}ApiKey` extension handlers.
 //!
 //! These methods let the client read/write the API key via the agent and
 //! drive the OAuth login flow. The agent is the single source of truth for
@@ -14,13 +14,13 @@ use crate::session::ExtMethodResult;
 #[tracing::instrument(skip_all, fields(method = %args.method))]
 pub async fn handle(agent: &MvpAgent, args: &acp::ExtRequest) -> ExtResult {
     match args.method.as_ref() {
-        "x.ai/auth/getBearerToken" => handle_get_bearer_token(agent).await,
-        "x.ai/getApiKey" => handle_get_api_key(),
-        "x.ai/setApiKey" => handle_set_api_key(args),
-        "x.ai/auth/submit_code" => handle_submit_code(agent, args),
-        "x.ai/auth/get_url" => handle_get_url(agent).await,
-        "x.ai/auth/logout" => handle_logout(agent, args).await,
-        "x.ai/auth/info" => handle_info(agent),
+        "kigi/auth/getBearerToken" => handle_get_bearer_token(agent).await,
+        "kigi/getApiKey" => handle_get_api_key(),
+        "kigi/setApiKey" => handle_set_api_key(args),
+        "kigi/auth/submit_code" => handle_submit_code(agent, args),
+        "kigi/auth/get_url" => handle_get_url(agent).await,
+        "kigi/auth/logout" => handle_logout(agent, args).await,
+        "kigi/auth/info" => handle_info(agent),
         _ => Err(acp::Error::method_not_found()),
     }
 }