§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test could previously reach the real api.moonshot.cn), and the outdated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/tests/scenarios/folder_trust_prompt.yaml

@@ -13,7 +13,7 @@ environment:
   env:
     - key: KIGI_FOLDER_TRUST
       value: "1"
-    # A self-built (unstamped) grok auto-trusts and never prompts; simulate a
+    # A self-built (unstamped) kigi auto-trusts and never prompts; simulate a
     # release build so the folder-trust prompt is actually evaluated.
     - key: KIGI_TEST_VERSION
       value: "0.0.0-sim"

crates/codegen/kigi-tui/tests/scenarios/mid_text_skill_token_echo.yaml

@@ -3,7 +3,7 @@ description: >
   A plain prompt referencing a skill mid-message
   ("great /test-skill do it") keeps the composer's teal token highlight in the
   scrollback echo after submit. The workspace seeds a repo-local
-  .grok/skills/test-skill/SKILL.md so the real shell advertises the skill; the
+  .kigi/skills/test-skill/SKILL.md so the real shell advertises the skill; the
   screenshots capture the styled composer (pre-submit) and the styled echo
   (post-submit) — the styled JSON artifacts carry the per-run fg colors for
   visual verification and demo material.
@@ -15,7 +15,7 @@ environment:
 workspace:
   git_init: true
   files:
-    ".grok/skills/test-skill/SKILL.md": "---\nname: test-skill\ndescription: Test skill for echo styling.\n---\n\nDo the thing.\n"
+    ".kigi/skills/test-skill/SKILL.md": "---\nname: test-skill\ndescription: Test skill for echo styling.\n---\n\nDo the thing.\n"
 mock:
   response: "MIDTEXT_SKILL_ECHO_DONE assistant reply after the mid-text skill prompt."
 steps: