§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test could previously reach the real api.moonshot.cn), and the outdated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-hooks/src/runner/command.rs

@@ -87,7 +87,7 @@ pub async fn run_command_hook(
     let mut cmd = if is_shell_command {
         // Refuse to spawn when the command interpolates an env var that
         // we can't resolve from any of: the runner's always-set vars, the
-        // per-hook extra_env (plugin vars), or Grok's own process env. The
+        // per-hook extra_env (plugin vars), or Kigi's own process env. The
         // alternative is letting sh expand the var to empty -- which then
         // produces a broken command, exits 127, and (for PreToolUse hooks)
         // fails closed with an opaque "exit code 127" reason. Catching it
@@ -287,7 +287,7 @@ pub(crate) const RUNNER_ALWAYS_SET_ENV: &[&str] = &[
 /// * the runner's always-set env vars (see [`RUNNER_ALWAYS_SET_ENV`]),
 /// * the per-hook `extra_env` map (set by the plugin adapter for plugin
 ///   hooks),
-/// * the Grok process's own environment (which is inherited by the child),
+/// * the Kigi process's own environment (which is inherited by the child),
 /// * local shell assignments inside the command itself (e.g. an
 ///   `INPUT=$(cat)` earlier in the string defines `INPUT` for the rest of
 ///   the command).