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/agent/mvp_agent/mod.rs

@@ -124,7 +124,6 @@ pub(crate) struct SessionSpawnOptions<'a> {
         crate::session::announcement_state::AnnouncementState,
     >,
     pub session_meta: Option<&'a acp::Meta>,
-    pub managed_mcp_expires_at: Option<chrono::DateTime<chrono::Utc>>,
     pub model_agent_type: Option<&'a str>,
     pub session_model_id: acp::ModelId,
     pub session_yolo_mode: bool,
@@ -260,7 +259,6 @@ pub(crate) fn chat_session_spawn_options<'a>(
         persisted_goal_mode: None,
         persisted_announcement_state: None,
         session_meta,
-        managed_mcp_expires_at: None,
         model_agent_type,
         session_model_id,
         session_yolo_mode,
@@ -591,8 +589,6 @@ pub struct MvpAgent {
     /// Local config.toml override for session registry (`[cli] session_registry`).
     /// `Some(true)` enables, `Some(false)` disables, `None` defers to remote settings.
     session_registry_local: Option<bool>,
-    /// Managed MCP configs and gateway tool catalog; lazily fetched.
-    managed_mcp_cache: crate::session::managed_mcp::ManagedMcpStateHandle,
     /// Agent-level MCP server state. LEADER-SAFE(shared): MCP servers are
     /// agent-scoped, not per-client.
     agent_mcp_state: std::sync::Arc<