§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test could previously reach the real api.moonshot.cn), and the outdated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/fixtures/historic_bash_cmds.txt

@@ -71,7 +71,7 @@ curl -LsSf "http://file-server.example.internal/cicd/example/install.sh?nocache"
 ! sudo du -shx /.Spotlight-V100 /.DocumentRevisions-V100 /private/var/vm /private/var/folders /cores /Library 2>/dev/null | sort -rh
 ### END
 ### CMD 21
-cat ~/.grok/config.toml | grep composer
+cat ~/.kigi/config.toml | grep composer
 ### END
 ### CMD 22
 KIGI_DEBUG_CONTEXT_WINDOW=100000 KIGI_AUTO_COMPACT_THRESHOLD_PERCENT=5 /tmp/pager-under-test -r 019e0000-0000-7000-8000-000000000001 -p 'reply with exactly: again' --model example-model --always-approve --no-leader > /tmp/compaction-repro/headless5.log 2>&1; echo EXIT=$? >> /tmp/compaction-repro/headless5.log
@@ -95,7 +95,7 @@ strings target/debug/kigi-tui | grep -c slash-mru-writer   # must print >=1\
 SSH_CONNECTION='10.0.0.1 51234 10.0.0.2 22' \\
 ### END
 ### CMD 29
-DYLD_FORCE_FLAT_NAMESPACE=1 DYLD_INSERT_LIBRARIES=/opt/homebrew/lib/faketime/libfaketime.1.dylib FAKETIME_TIMESTAMP_FILE=/tmp/ft.rc FAKETIME_NO_CACHE=1 FAKETIME_DONT_FAKE_MONOTONIC=1 /tmp/pager-date-test --model grok-build --always-approve --no-leader
+DYLD_FORCE_FLAT_NAMESPACE=1 DYLD_INSERT_LIBRARIES=/opt/homebrew/lib/faketime/libfaketime.1.dylib FAKETIME_TIMESTAMP_FILE=/tmp/ft.rc FAKETIME_NO_CACHE=1 FAKETIME_DONT_FAKE_MONOTONIC=1 /tmp/pager-date-test --model kigi --always-approve --no-leader
 ### END
 ### CMD 30
 DYLD_FORCE_FLAT_NAMESPACE=1 DYLD_INSERT_LIBRARIES=/opt/homebrew/lib/faketime/libfaketime.1.dylib FAKETIME_TIMESTAMP_FILE=/tmp/ft.rc FAKETIME_NO_CACHE=1 FAKETIME_DONT_FAKE_MONOTONIC=1 /tmp/pager-date-test --always-approve --no-leader