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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -5,8 +5,8 @@
 //! actors) plus recently-touched on-disk (`Dormant`) sessions. Clients read it
 //! two ways:
 //!
-//!   - request/response `x.ai/sessions/list` → `{ "sessions": [RosterEntry, …] }`
-//!   - broadcast notification `x.ai/sessions/changed` →
+//!   - request/response `kigi/sessions/list` → `{ "sessions": [RosterEntry, …] }`
+//!   - broadcast notification `kigi/sessions/changed` →
 //!     `{ "upserted": [RosterEntry, …], "removed": ["sess-abc", …] }`
 //!
 //! The wire shape is intentionally small and current-state only — no event
@@ -76,13 +76,13 @@ pub struct RosterEntry {
     pub origin: RosterOrigin,
 }
 
-/// Response payload for `x.ai/sessions/list`.
+/// Response payload for `kigi/sessions/list`.
 #[derive(Serialize, Deserialize, Clone, Debug, Default)]
 pub struct RosterListResponse {
     pub sessions: Vec<RosterEntry>,
 }
 
-/// Params payload for the `x.ai/sessions/changed` broadcast notification.
+/// Params payload for the `kigi/sessions/changed` broadcast notification.
 #[derive(Serialize, Deserialize, Clone, Debug, Default)]
 pub struct RosterChanged {
     #[serde(default)]
@@ -92,8 +92,8 @@ pub struct RosterChanged {
 }
 
 /// JSON-RPC method names for the roster API.
-pub const SESSIONS_LIST_METHOD: &str = "x.ai/sessions/list";
-pub const SESSIONS_CHANGED_METHOD: &str = "x.ai/sessions/changed";
+pub const SESSIONS_LIST_METHOD: &str = "kigi/sessions/list";
+pub const SESSIONS_CHANGED_METHOD: &str = "kigi/sessions/changed";
 
 /// Merge live `resident` rows with on-disk `summaries` into the sorted roster.
 /// Pure, so it is unit-testable without disk or a live actor.
@@ -173,7 +173,7 @@ mod merge_roster_tests {
             title: None,
             cwd: format!("/live/{id}"),
             is_worktree: false,
-            model_id: Some("grok-4".into()),
+            model_id: Some("kigi-4".into()),
             reasoning_effort: None,
             yolo: false,
             activity,