M2 audit: excise the Computer Hub stack — Kigi's last remote-cloud surface

Removed root-and-branch for the zero-egress guarantee (the hub was xAI's
remote-workspace/cloud-sandbox service):

- Crates deleted: kigi-computer-hub-core, kigi-computer-hub-sdk,
  kigi-computer-hub-mcp-adapter, kigi-workspace-client (hub-proxied
  workspace RPC client), and kigi-tracing (its sole network path was the
  OTLP gRPC exporter; zero consumers remained). kigi-tracing-macros
  (purely local) stays.
- kigi-workspace: every hub surface deleted — hub server/channel/auth,
  HITL-over-hub permissions, donation/metrics pumps, file upload RPCs,
  hub tool-snapshot merge (resolve pipeline is MCP-only now),
  WorkspaceOps::Proxy. Local worktrees, sessions, leader IPC, MCP, and
  the ACP permission prompt path are untouched; LocalRegistry re-homed
  into kigi-tool-runtime on the existing ToolDyn types so in-process
  tool dispatch is unchanged.
- kigi-shell: leader workspace-exposure control surface (incl. the
  wss://computer-hub... URL), [hub] config, ObservabilityBridge, hub
  WebSocket proxy, dead OTLP config knobs. ClientMode::Headless (never
  constructed) removed.
- kigi-tui/bin: hidden `kigi workspace` command removed (`kigi
  worktree` stays).
- Renames: --xai-api-base-url → --api-base-url / KIGI_API_BASE_URL /
  [endpoints] api_base_url (serde alias keeps old configs working; the
  flag feeds BYOK/custom-endpoint routing, not main inference);
  grok_version → kigi_version in inspect/models-cache/trace metadata
  (old caches self-heal via version-mismatch refetch).
- Dependency tree: dropped fastrace*, opentelemetry-otlp/http/proto,
  tokio-tungstenite from the workspace; fixed the 4 real useless_format
  violations the fastrace lint allowance was masking and removed the
  allowance.
- marketplaceAllowlist kept: it gates the LOCAL plugin-marketplace
  feature, not an xAI service.

Known §9 leftover (deliberate, for the M3 sweep): the BYOK default base
URL string. Gates: workspace check/clippy 0/0, fmt, deny ok; suites
green (workspace 1042, shell 4918, tui 6634, tools 2608, tool-runtime
47, mcp 154).

crates/codegen/kigi-shell/src/agent/models.rs

@@ -1323,7 +1323,7 @@ const CACHE_TTL: std::time::Duration = std::time::Duration::from_secs(300);
 struct ModelsCache {
     fetched_at: DateTime<Utc>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    grok_version: Option<String>,
+    kigi_version: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     auth_method: Option<CacheAuthMethod>,
     /// Models-list URL this catalog was fetched from
@@ -1418,7 +1418,7 @@ impl ModelsCacheManager {
     ) -> Option<ModelsCache> {
         let data = std::fs::read(&self.path).ok()?;
         let cache: ModelsCache = serde_json::from_slice(&data).ok()?;
-        if cache.grok_version.as_deref() != Some(kigi_version::VERSION) {
+        if cache.kigi_version.as_deref() != Some(kigi_version::VERSION) {
             tracing::debug!("models cache version mismatch");
             return None;
         }
@@ -1447,7 +1447,7 @@ impl ModelsCacheManager {
     ) {
         let cache = ModelsCache {
             fetched_at: Utc::now(),
-            grok_version: Some(kigi_version::VERSION.to_string()),
+            kigi_version: Some(kigi_version::VERSION.to_string()),
             auth_method: Some(auth_method),
             origin: Some(origin.to_string()),
             etag: etag.map(|s| s.to_string()),
@@ -3064,7 +3064,7 @@ mod tests {
         let auth_method = mgr.inner.fetch_auth.read().cache_auth_method();
         let stale = ModelsCache {
             fetched_at: Utc::now() - ChronoDuration::seconds(3600),
-            grok_version: Some(kigi_version::VERSION.to_string()),
+            kigi_version: Some(kigi_version::VERSION.to_string()),
             auth_method: Some(auth_method),
             origin: Some(mgr.cache_origin()),
             etag: Some("etag-stale".into()),
@@ -3140,7 +3140,7 @@ mod tests {
         let auth_method = mgr.inner.fetch_auth.read().cache_auth_method();
         let legacy = ModelsCache {
             fetched_at: Utc::now(),
-            grok_version: Some(kigi_version::VERSION.to_string()),
+            kigi_version: Some(kigi_version::VERSION.to_string()),
             auth_method: Some(auth_method),
             origin: None,
             etag: Some("etag-legacy".into()),
@@ -4100,7 +4100,7 @@ mod tests {
         let cache = ModelsCacheManager::new();
         let stale = ModelsCache {
             fetched_at: Utc::now() - ChronoDuration::seconds(86_400),
-            grok_version: Some(kigi_version::VERSION.to_string()),
+            kigi_version: Some(kigi_version::VERSION.to_string()),
             auth_method: Some(CacheAuthMethod::Platforms),
             origin: Some(origin),
             etag: None,
@@ -4187,7 +4187,7 @@ mod tests {
         let cache = ModelsCacheManager::new();
         cache.atomic_write(&ModelsCache {
             fetched_at: Utc::now() - ChronoDuration::seconds(86_400),
-            grok_version: Some(kigi_version::VERSION.to_string()),
+            kigi_version: Some(kigi_version::VERSION.to_string()),
             auth_method: Some(CacheAuthMethod::Platforms),
             origin: Some(with_key_origin),
             etag: None,