§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test could previously reach the real api.moonshot.cn), and the outdated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/app/dispatch/prompt.rs

@@ -32,7 +32,7 @@ pub(super) fn consume_chat_kind(app: &mut AppView) -> bool {
 /// The prompt is always pushed to the queue first. If the agent is idle
 /// (and has a session), `maybe_drain_queue` pops the front prompt and
 /// sends it in the same dispatch call — no deferred ticks.
-/// Start (if needed) and submit the initial prompt from `grok "<prompt>"`.
+/// Start (if needed) and submit the initial prompt from `kigi "<prompt>"`.
 ///
 /// Shared by the TUI startup path (already authenticated) and the post-login
 /// `AuthComplete` path (deferred via `deferred_startup.prompt`). It does nothing
@@ -511,7 +511,7 @@ pub(super) fn dispatch_send_prompt_inner(
         // immediately instead of being held in the local drip-feed queue. The
         // agent appends it to its authoritative `pending_inputs` (no concurrent
         // turn starts — validated keystone) and drives the drain via
-        // `x.ai/queue/changed`. We render an optimistic echo into the shared
+        // `kigi/queue/changed`. We render an optimistic echo into the shared
         // queue keyed by `prompt_id`; the broadcast reconciles it by id.
         //
         // The IDLE case is unchanged (falls through to the local path below,
@@ -930,7 +930,7 @@ pub(super) fn handle_prompt_response(
                 // Server-authoritative queue lifecycle: this prompt's RPC
                 // resolved without becoming the running turn (removed,
                 // cancelled, rewound). Retire its optimistic echo so a
-                // later `x.ai/queue/changed` broadcast can't re-pin a
+                // later `kigi/queue/changed` broadcast can't re-pin a
                 // stale placeholder and reorder the queue.
                 if let Some(sid) = agent.session.session_id.as_ref().map(|s| s.0.to_string()) {
                     retire_optimistic_echo(
@@ -1171,7 +1171,7 @@ pub(super) fn handle_prompt_response(
                 // title into the body automatically.
                 let notif_title = session_name
                     .map(|s| s.to_string())
-                    .unwrap_or_else(|| "Grok".into());
+                    .unwrap_or_else(|| "Kigi".into());
 
                 app.deferred_notification = Some((
                     NotificationEvent {