§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test could previously reach the real api.moonshot.cn), and the outdated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/common/kigi-compaction/src/code_compaction/assemble.rs

@@ -1,4 +1,4 @@
-//! Compacted-history assembly (grok-build's rebuild structure, generic).
+//! Compacted-history assembly (kigi's rebuild structure, generic).
 //!
 //! Moved from `kigi-chat-state::compaction_utils::build_compacted_history` and
 //! made generic over a write-side item factory so any harness can assemble
@@ -8,7 +8,7 @@
 //! [SP, UP', AGENTS_MD?, UQ_last?, recent…, summary, reminder?]
 //! ```
 //!
-//! grok-build is the canonical harness. The summary carrier text is built by
+//! kigi is the canonical harness. The summary carrier text is built by
 //! [`super::summary::format_compact_summary_content`].
 
 use crate::item::CompactionItemFactory;
@@ -80,7 +80,7 @@ pub fn assemble_compacted_history<T: CompactionItemFactory>(
         compacted.push(T::new_user(wrap_user_query(last_query.as_str())));
     }
 
-    // grok-build keeps the legacy `<user_query>`-wrapped continuation text and
+    // kigi keeps the legacy `<user_query>`-wrapped continuation text and
     // appends the transcript hint after the continuation summary.
     let mut formatted_summary = format_compact_summary_content(&parts.compaction_summary);
     if let Some(ref hint) = parts.transcript_hint {
@@ -145,7 +145,7 @@ mod tests {
     }
 
     #[test]
-    fn grok_build_order_recent_before_summary() {
+    fn kigi_order_recent_before_summary() {
         let recent = vec![MockItem::Recent("a1".into()), MockItem::Recent("t1".into())];
         let out = assemble_compacted_history(parts(recent));
         // [sys, prefix, agents_md, query, a1, t1, summary, reminder]