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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -534,7 +534,7 @@ pub(crate) fn builtin_commands(availability: CommandAvailability) -> Vec<acp::Av
         .collect()
 }
 
-// ── x.ai/commands/list ext method ────────────────────────────────
+// ── kigi/commands/list ext method ────────────────────────────────
 
 #[derive(serde::Deserialize)]
 pub(crate) struct ListCommandsRequest {
@@ -731,7 +731,7 @@ impl BuiltinAction {
 /// How to rewrite the user's prompt when a slash command resolves to a skill.
 ///
 /// - `RewriteToRun` (default): replace `/foo args` with `"run /foo args"`,
-///   matching today's Grok Build flow that calls our dedicated `skill` tool.
+///   matching today's Kigi flow that calls our dedicated `skill` tool.
 /// - `Passthrough`: leave the prompt verbatim. Some templates use this —
 ///   the model is trained to spot a leading `/<name>`, look it up in the
 ///   `<agent_skills>` listing, and call the Read tool on `fullPath`.
@@ -1081,7 +1081,7 @@ fn parse_slash_prefix(prompt_blocks: &[acp::ContentBlock]) -> Option<(&str, &str
 /// default: the model derives the cadence from the request and asks when none
 /// is given.
 fn build_loop_prompt_blocks(args: &str) -> Vec<acp::ContentBlock> {
-    use kigi_tools::implementations::grok_build::{loop_schedule_instruction, loop_usage_message};
+    use kigi_tools::implementations::kigi::{loop_schedule_instruction, loop_usage_message};
 
     let text = if args.trim().is_empty() {
         loop_usage_message().to_string()
@@ -1685,9 +1685,7 @@ mod tests {
     #[test]
     fn loop_prompt_matches_pager_wording() {
         // The shell and pager must stay textually identical so they don't drift.
-        use kigi_tools::implementations::grok_build::{
-            loop_schedule_instruction, loop_usage_message,
-        };
+        use kigi_tools::implementations::kigi::{loop_schedule_instruction, loop_usage_message};
         assert_eq!(loop_text(""), loop_usage_message());
         assert_eq!(
             loop_text("2h run tests"),