§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test could previously reach the real api.moonshot.cn), and the outdated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-tui/src/notifications/config.rs

@@ -80,7 +80,7 @@ impl Default for TitleConfig {
                 TitleItem::Spinner,
                 TitleItem::Activity,
                 TitleItem::SessionName,
-                TitleItem::Grok,
+                TitleItem::Kigi,
             ],
         }
     }
@@ -95,7 +95,7 @@ pub enum TitleItem {
     Cwd,
     Model,
     TurnTimer,
-    Grok,
+    Kigi,
     ActionRequired,
 }
 
@@ -177,11 +177,11 @@ session_recap_threshold_secs = 30
 # Set the terminal/tab title to reflect agent state.
 enabled = true
 # Items shown in the title. Options: action-required, spinner, activity,
-# session-name, cwd, model, turn-timer, grok
-items = [\"action-required\", \"spinner\", \"activity\", \"session-name\", \"grok\"]
+# session-name, cwd, model, turn-timer, kigi
+items = [\"action-required\", \"spinner\", \"activity\", \"session-name\", \"kigi\"]
 
 # [[ui.notifications.hooks]]
-# command = \"terminal-notifier -title 'Grok' -message '$KIGI_MESSAGE'\"
+# command = \"terminal-notifier -title 'Kigi' -message '$KIGI_MESSAGE'\"
 # events = [\"turn_complete\", \"approval_required\"]
 # only_unfocused = true
 # timeout_secs = 10
@@ -210,7 +210,7 @@ mod tests {
             session_recap_threshold_secs: 90,
             title: TitleConfig {
                 enabled: false,
-                items: vec![TitleItem::Grok, TitleItem::Cwd],
+                items: vec![TitleItem::Kigi, TitleItem::Cwd],
             },
             hooks: vec![NotificationHook {
                 command: "notify-send".into(),