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/session/acp_session_impl/spawn.rs

@@ -251,34 +251,8 @@ pub(crate) async fn spawn_session_actor(
             .as_ref()
             .map(kigi_workspace::permission::resolution::deny_read_globs_from_config)
             .unwrap_or_default();
-        let hub_permission = if kigi_workspace::permission::hitl_permission_live_enabled() {
-            let server = match workspace_ops.workspace_handle() {
-                Some(handle) => handle.hub_server_blocking().await,
-                None => None,
-            };
-            let transport = server
-                .and_then(|server| {
-                    kigi_workspace::permission::ToolServerPermissionTransport::from_session_id(
-                        server,
-                        session_info.id.0.as_ref(),
-                    )
-                })
-                .map(|t| {
-                    std::sync::Arc::new(t)
-                        as std::sync::Arc<dyn kigi_workspace::permission::PermissionHookTransport>
-                });
-            if transport.is_none() {
-                tracing::debug!(
-                    session_id = % session_info.id.0,
-                    "hitl permission live enabled but no remote transport available; using local prompt"
-                );
-            }
-            transport
-        } else {
-            None
-        };
         let (permissions, _permission_events_rx) =
-            kigi_workspace::permission::spawn_permission_manager_with_hub(
+            kigi_workspace::permission::spawn_permission_manager(
                 session_info.id.clone(),
                 gateway.clone(),
                 tool_context.cwd.clone(),
@@ -289,7 +263,6 @@ pub(crate) async fn spawn_session_actor(
                 session_yolo_mode,
                 session_client_identifier.clone(),
                 crate::util::config::remember_tool_approvals_from_disk(),
-                hub_permission,
             );
         if crate::util::config::auto_mode_session_active(
             crate::util::config::auto_permission_mode_enabled_from_disk(),
@@ -975,11 +948,6 @@ pub(crate) async fn spawn_session_actor(
     let (goal_update_tx, goal_update_rx) = tokio::sync::mpsc::unbounded_channel::<
         kigi_tools::implementations::grok_build::update_goal::UpdateGoalEnvelope,
     >();
-    let obs_bridge = {
-        let sid = kigi_tool_protocol::SessionId::new(&*session_info.id.0)
-            .unwrap_or_else(|_| kigi_tool_protocol::SessionId::new("unknown").expect("valid"));
-        kigi_computer_hub_sdk::ObservabilityBridge::new(None, sid)
-    };
     let mut effective_config = crate::config::load_effective_config()
         .ok()
         .and_then(|raw| crate::agent::config::Config::new_from_toml_cfg(&raw).ok())
@@ -1199,7 +1167,6 @@ pub(crate) async fn spawn_session_actor(
         events: crate::session::events::EventTracker::new(
             &crate::session::persistence::session_dir(&session_info),
         ),
-        observability_bridge: obs_bridge,
         current_turn_number: std::cell::Cell::new(0),
         last_recap_main_turn: std::cell::Cell::new(0),
         recap_in_flight: std::cell::Cell::new(false),