§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test could previously reach the real api.moonshot.cn), and the outdated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-chat-state/src/compaction_utils.rs

@@ -598,7 +598,7 @@ impl CompactionStateContext {
     /// For a sub-agent with
     /// a single real user turn, `recent_messages` is the ENTIRE working
     /// transcript, and keeping it frees almost nothing while re-cueing the
-    /// model to re-read the same files. grok-build retains
+    /// model to re-read the same files. kigi retains
     /// `recent_messages` so the model keeps verbatim tool context.
     pub fn for_compaction(&self) -> Self {
         Self {
@@ -803,17 +803,17 @@ pub struct CompactedHistoryInput<'a> {
     /// summary. `None` means no state reminder is appended.
     pub system_reminder: Option<String>,
     /// When `true`, emit the compaction summary *before* recent messages.
-    /// When `false` (the default), recent messages come first (grok-build
+    /// When `false` (the default), recent messages come first (kigi
     /// ordering).
     pub summary_before_recent: bool,
     /// Pre-built transcript hint appended to the summary (caller builds it via
     /// [`crate::CompactionMode::transcript_hint`] or
     /// [`format_transcript_location`]). `None` to omit. Appended to BOTH the
-    /// carrier and the grok-build summary.
+    /// carrier and the kigi summary.
     pub transcript_hint: Option<String>,
     /// Number of summaries generated so far for this user query, *including*
     /// the one being built. Rendered verbatim into the carrier's
-    /// "Total summaries generated so far …" footer. Ignored by the grok-build
+    /// "Total summaries generated so far …" footer. Ignored by the kigi
     /// (`summary_before_recent == false`) path. Callers that don't track a
     /// counter pass `1`.
     pub summary_count: u64,
@@ -2679,7 +2679,7 @@ actual user question";
                         arguments: r#"{"target_file":"src/lib.rs"}"#.into(),
                     },
                 ],
-                model_id: Some("grok-3".to_string()),
+                model_id: Some("kigi-3".to_string()),
                 model_fingerprint: None,
                 reasoning_effort: None,
             }),
@@ -2712,7 +2712,7 @@ actual user question";
                         arguments: r#"{"command":"cargo test"}"#.into(),
                     },
                 ],
-                model_id: Some("grok-3".to_string()),
+                model_id: Some("kigi-3".to_string()),
                 model_fingerprint: None,
                 reasoning_effort: None,
             }),
@@ -3390,7 +3390,7 @@ The user asked to read main.rs and lib.rs. main.rs prints hello world, lib.rs ha
         assert!(
             kept.iter()
                 .any(|i| matches!(i, ConversationItem::Reasoning(_))),
-            "reasoning must be kept when strip_reasoning = false (Grok backends)"
+            "reasoning must be kept when strip_reasoning = false (Kigi backends)"
         );
         let stripped = prepare_conversation_for_verbatim_summarization(mk(), true);
         assert!(