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test could previously reach the real api.moonshot.cn), and the outdated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

@@ -152,7 +152,7 @@ fn trust_prompt(subject: &str, source_arg: &str) -> String {
         "Installing {subject} requires confirmation.\n\
          Plugins can run hooks, MCP servers, and skills on your machine, so installation needs explicit trust.\n\
          \n\
-         To proceed, re-run with --trust:\n  grok plugin install {source_arg} --trust"
+         To proceed, re-run with --trust:\n  kigi plugin install {source_arg} --trust"
     )
 }
 
@@ -277,7 +277,7 @@ fn cmd_uninstall(name: &str, confirm: bool, keep_data: bool) -> Result<()> {
             "Plugin \"{name}\" belongs to repo \"{repo_key}\" which also contains:\n\
              {}\n\n\
              Uninstalling will remove all {total} plugin(s). To proceed:\n\
-               grok plugin uninstall {name} --confirm",
+               kigi plugin uninstall {name} --confirm",
             other_plugins
                 .iter()
                 .map(|p| format!("  - {p}"))
@@ -421,7 +421,7 @@ fn cmd_validate(path: &str) -> Result<()> {
         }
         Ok(ManifestLoadResult::NotFound) => {
             println!(
-                "No plugin.json found. Grok discovers skills, agents, and hooks \
+                "No plugin.json found. Kigi discovers skills, agents, and hooks \
                  automatically from standard directories. A manifest is only needed \
                  for custom paths or metadata."
             );
@@ -517,7 +517,7 @@ mod tests {
             ),
             "{git}"
         );
-        assert!(git.ends_with("  grok plugin install u/r --trust"), "{git}");
+        assert!(git.ends_with("  kigi plugin install u/r --trust"), "{git}");
         let local = trust_prompt("from directory /tmp/p", "./p");
         assert!(
             local.starts_with("Installing from directory /tmp/p requires confirmation."),