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-config-types/src/lib.rs

@@ -694,11 +694,6 @@ pub struct RemoteSettings {
     /// See `Config::resolve_image_edit`.
     #[serde(default)]
     pub imagine_tools_disabled: Option<Vec<String>>,
-    /// remote settings gate for the `grok workspace` CLI command (Computer Hub
-    /// workspace exposure), from `grok_build_settings.workspace_command_enabled`.
-    /// `Some(true)` enables it; `None`/`Some(false)` (the default) keep it off.
-    #[serde(default)]
-    pub workspace_command_enabled: Option<bool>,
     /// Master switch for jemalloc heap sampling + threshold dumps.
     /// `Some(true)` enables, `Some(false)` kill-switch, `None` = client default off.
     #[serde(default)]
@@ -1308,24 +1303,6 @@ mod tests {
         assert_eq!(s.folder_trust_enabled, None);
     }
     #[test]
-    fn remote_settings_workspace_command_enabled_present() {
-        let json = r#"{"workspace_command_enabled": true}"#;
-        let s: RemoteSettings = serde_json::from_str(json).unwrap();
-        assert_eq!(s.workspace_command_enabled, Some(true));
-    }
-    #[test]
-    fn remote_settings_workspace_command_enabled_false() {
-        let json = r#"{"workspace_command_enabled": false}"#;
-        let s: RemoteSettings = serde_json::from_str(json).unwrap();
-        assert_eq!(s.workspace_command_enabled, Some(false));
-    }
-    #[test]
-    fn remote_settings_workspace_command_enabled_absent() {
-        let json = r#"{}"#;
-        let s: RemoteSettings = serde_json::from_str(json).unwrap();
-        assert_eq!(s.workspace_command_enabled, None);
-    }
-    #[test]
     fn remote_settings_permission_mode_deserializes() {
         let s: RemoteSettings = serde_json::from_str(r#"{"permission_mode": "auto"}"#).unwrap();
         assert_eq!(s.permission_mode.as_deref(), Some("auto"));