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-workspace/src/permission/prompter.rs

@@ -321,9 +321,6 @@ pub struct AcpPrompter {
     /// at decision-time through it. `EventWriter::noop()` when events recording
     /// is disabled (the default for the permission scaffolding's own tests).
     event_writer: EventWriter,
-    /// Server permission transport: when set, [`request`](Self::request) asks chat for the
-    /// decision over the server; `None` keeps the local prompt.
-    hub_permission: Option<Arc<dyn crate::permission::PermissionHookTransport>>,
     /// When `false` (default, fail-safe), the per-tool "Always allow …" options
     /// are stripped (see [`REMEMBER_TOOL_APPROVALS_GATED_IDS`]).
     remember_tool_approvals: bool,
@@ -496,7 +493,6 @@ impl AcpPrompter {
             // must NOT double-emit. A workspace-server-side caller that owns the
             // per-session `events.jsonl` opts in via [`with_event_writer`].
             event_writer: EventWriter::noop(),
-            hub_permission: None,
             // Fail-safe default; opt in via `with_remember_tool_approvals`.
             remember_tool_approvals: false,
         }
@@ -509,16 +505,6 @@ impl AcpPrompter {
         self
     }
 
-    /// Route the permission prompt to chat over the server when `Some`;
-    /// `None` keeps the local prompt.
-    pub fn with_hub_permission(
-        mut self,
-        hub_permission: Option<Arc<dyn crate::permission::PermissionHookTransport>>,
-    ) -> Self {
-        self.hub_permission = hub_permission;
-        self
-    }
-
     /// Attach a per-session `events.jsonl` writer so [`request`](Self::request)
     /// records `PermissionRequested` / `PermissionResolved`. Used by the
     /// workspace-server permission path (which owns the session log); the shell
@@ -737,41 +723,29 @@ impl AcpPrompter {
             prompt_start,
         };
 
-        let outcome = match &self.hub_permission {
-            // Route the prompt to chat over the server (see
-            // `ToolServerPermissionTransport` for the await/release contract).
-            Some(transport) => {
-                crate::permission::hub_permission::request_permission_via_hub(
-                    transport.as_ref(),
-                    access,
-                    tool_call_update.tool_call_id.0.as_ref(),
-                )
-                .await
-            }
-            None => {
-                let permission_options = self.build_options(access);
-                let req = acp::RequestPermissionRequest::new(
-                    self.session_id.clone(),
-                    tool_call_update.clone(),
-                    permission_options.values().cloned().collect(),
-                )
-                .meta(self.bash_selection_meta(access));
-                match self.gateway.request_permission(req).await {
-                    Ok(resp) => match resp.outcome {
-                        acp::RequestPermissionOutcome::Cancelled => PromptOutcome::Cancelled,
-                        acp::RequestPermissionOutcome::Selected(selected) => map_selected_outcome(
-                            &permission_options,
-                            &selected.option_id,
-                            resp.meta.as_ref(),
-                            access,
-                        ),
-                        // TODO(acp-0.10): `RequestPermissionOutcome` is #[non_exhaustive].
-                        _ => PromptOutcome::Error("unknown permission outcome".to_owned()),
-                    },
-                    Err(e) => {
-                        tracing::error!(?e, "failed to request permission");
-                        PromptOutcome::Error("failed to request permission".to_owned())
-                    }
+        let outcome = {
+            let permission_options = self.build_options(access);
+            let req = acp::RequestPermissionRequest::new(
+                self.session_id.clone(),
+                tool_call_update.clone(),
+                permission_options.values().cloned().collect(),
+            )
+            .meta(self.bash_selection_meta(access));
+            match self.gateway.request_permission(req).await {
+                Ok(resp) => match resp.outcome {
+                    acp::RequestPermissionOutcome::Cancelled => PromptOutcome::Cancelled,
+                    acp::RequestPermissionOutcome::Selected(selected) => map_selected_outcome(
+                        &permission_options,
+                        &selected.option_id,
+                        resp.meta.as_ref(),
+                        access,
+                    ),
+                    // TODO(acp-0.10): `RequestPermissionOutcome` is #[non_exhaustive].
+                    _ => PromptOutcome::Error("unknown permission outcome".to_owned()),
+                },
+                Err(e) => {
+                    tracing::error!(?e, "failed to request permission");
+                    PromptOutcome::Error("failed to request permission".to_owned())
                 }
             }
         };