§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test could previously reach the real api.moonshot.cn), and the outdated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-tool-protocol/tests/tool_id_derivation.rs

@@ -26,10 +26,8 @@ fn bare_name_derives_to_tool_id_without_namespace() {
 
 #[test]
 fn namespaced_name_derives_to_namespaced_tool_id() {
-    let derived = entry("read_file", Some("GrokBuild"))
-        .derive_tool_id()
-        .unwrap();
-    assert_eq!(derived, ToolId::new("GrokBuild:read_file").unwrap());
+    let derived = entry("read_file", Some("Kigi")).derive_tool_id().unwrap();
+    assert_eq!(derived, ToolId::new("Kigi:read_file").unwrap());
 }
 
 #[test]
@@ -58,9 +56,9 @@ fn empty_name_yields_empty_id_error() {
 #[test]
 fn duplicate_derivations_in_a_batch_are_detectable() {
     let batch = [
-        entry("read_file", Some("GrokBuild")),
-        entry("write_file", Some("GrokBuild")),
-        entry("read_file", Some("GrokBuild")),
+        entry("read_file", Some("Kigi")),
+        entry("write_file", Some("Kigi")),
+        entry("read_file", Some("Kigi")),
     ];
 
     let mut seen = std::collections::HashMap::new();
@@ -76,15 +74,13 @@ fn duplicate_derivations_in_a_batch_are_detectable() {
     }
     assert_eq!(duplicates.len(), 1, "exactly one duplicate id expected");
     let (id, indices) = &duplicates[0];
-    assert_eq!(id, &ToolId::new("GrokBuild:read_file").unwrap());
+    assert_eq!(id, &ToolId::new("Kigi:read_file").unwrap());
     assert_eq!(indices, &vec![0, 2]);
 }
 
 #[test]
 fn derivation_does_not_collide_across_namespaces() {
-    let a = entry("read_file", Some("GrokBuild"))
-        .derive_tool_id()
-        .unwrap();
+    let a = entry("read_file", Some("Kigi")).derive_tool_id().unwrap();
     let b = entry("read_file", Some("github")).derive_tool_id().unwrap();
     let c = entry("read_file", None).derive_tool_id().unwrap();
     assert_ne!(a, b);