M2 audit: excise managed connectors and xAI media-gen tools

Managed connectors (grok.com MCP admin) removed root-and-branch:
- The managed-MCP fetch/injection pipeline is gone, including the whole
  kigi-shell-session-support crate (managed-config fetch client, gateway
  tool catalog + dispatch, header injection, refresh task), reactive
  managed re-auth, mcp_doctor's grok.com-source discovery, and the
  [managed_mcps] config surface.
- TUI: the 'Managed by grok.com' section, connectors URL/deep-link,
  Action::OpenManagedConnectors, and session_team_id are gone. Local MCP
  management (list/toggle/add/remove/auth/tools) is fully intact.
- Kept as LOCAL policy: managed-settings.json MCP allow/deny enforcement,
  the multi-source local MCP merge, folder-trust gating. PluginOrigin
  Project/User labels kept (they tag locally discovered plugin dirs).

imagine/media-gen tools (xAI image/video generation) removed:
- image_gen, image_edit, video_gen, image_to_video, reference_to_video
  implementations, registrations, ToolKind/ToolInput/Output variants
  (serde-safe), config plumbing end to end, ZDR video machinery,
  /imagine + /imagine-video commands and guidance text, the bundled
  imagine skill (added to legacy cleanup so user installs delete it),
  and the media-gen render path.
- Kept: image INPUT (paste/attach, [Image #N] meta, pdf/image fetch,
  clipboard wrap), generic media-ref rendering, and the generic tool
  401-retry machinery (tests renamed, assertions unweakened).
- deploy_app stays: it is a permanently-disabled local stub deploying
  nowhere.

121 files changed, 8 deleted. Gates: workspace check/clippy 0/0, fmt,
deny ok; suites green (tools 2554, shell 4862, tui 6608, workspace
1042). Remaining grok.com strings live only in the auth-method ids and
changelog archives (§9/M3 sweep).

crates/codegen/kigi-shell/src/session/commands.rs

@@ -346,7 +346,7 @@ pub enum SessionCommand {
         server_name: String,
         enabled: bool,
         /// Fully-formed server config to add when re-enabling. Built by the
-        /// caller via `merge_managed_mcp_servers` (with OAuth headers injected).
+        /// caller via `merge_managed_mcp_servers`.
         /// `None` when disabling.
         server_config: Option<acp::McpServer>,
         respond_to: oneshot::Sender<Result<(), acp::Error>>,
@@ -357,17 +357,12 @@ pub enum SessionCommand {
         server_name: String,
         tool_name: String,
         enabled: bool,
-        is_managed_gateway: bool,
         respond_to: oneshot::Sender<Result<(), acp::Error>>,
     },
     /// Read MCP status: which servers are configured, which clients are healthy, what tools.
     GetMcpStatus {
         respond_to: oneshot::Sender<crate::extensions::mcp::McpStatusSnapshot>,
     },
-    GetManagedGatewayDisabledTools {
-        respond_to:
-            oneshot::Sender<std::collections::HashMap<String, std::collections::HashSet<String>>>,
-    },
     /// Snapshot the session's live MCP client pool for subagent inheritance.
     SnapshotMcpPool {
         respond_to: oneshot::Sender<Option<crate::session::mcp_servers::SharedMcpPool>>,