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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -152,7 +152,7 @@ fn draw(f: &mut ratatui::Frame, app: &App) {
         )),
         Line::from(""),
         Line::from(
-            "I'm Grok Build, an interactive CLI agent built to help with software engineering tasks.",
+            "I'm Kigi, an interactive CLI agent built to help with software engineering tasks.",
         ),
         Line::from(
             "This sample is here so you can drag over real text while watching raw mouse events.",

crates/codegen/kigi-tui/src/bin/question_view_playground.rs

@@ -4,7 +4,7 @@ use std::time::Duration;
 use crossterm::ExecutableCommand;
 use crossterm::event::{self, Event, KeyCode, KeyEvent, KeyModifiers};
 use crossterm::terminal::{self, EnterAlternateScreen, LeaveAlternateScreen};
-use kigi_tools::implementations::grok_build::ask_user_question::{Question, QuestionOption};
+use kigi_tools::implementations::kigi::ask_user_question::{Question, QuestionOption};
 use kigi_tui::theme::Theme;
 use kigi_tui::views::prompt_widget::StashedPrompt;
 use kigi_tui::views::question_view::{

crates/codegen/kigi-tui/src/bin/scrollback_selection_playground.rs

@@ -84,7 +84,7 @@ impl App {
             "I am thinking through how to answer your question before responding.",
         ));
         scrollback.push_block(RenderBlock::agent_message(
-            "I'm Grok Build, an interactive CLI agent built to help with software engineering tasks like coding, debugging, refactoring, and exploring codebases.",
+            "I'm Kigi, an interactive CLI agent built to help with software engineering tasks like coding, debugging, refactoring, and exploring codebases.",
         ));
         scrollback.push_block(RenderBlock::agent_message(
             "Try drag-selecting text. Double-click toggles fold by default; set Text selection → Word select for double-click word / triple-click line.",