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/subagent/mod.rs

@@ -144,7 +144,6 @@ pub(crate) struct SubagentSpawnContext {
     /// context is built (an async snapshot from the parent session actor).
     pub client_hooks: crate::extensions::hooks::ClientHooks,
     pub sampling_config: kigi_sampler::SamplerConfig,
-    pub managed_mcp_proxy_base_url: String,
     /// The staging auth header value propagated from the parent. Used
     /// when materialising subagent `SamplerConfig`s for auth-flow tracking
     /// and for `inject_url_derived_headers` in the construction helpers.
@@ -209,10 +208,6 @@ pub(crate) struct SubagentSpawnContext {
     pub web_search_config: kigi_tools::implementations::WebSearchConfig,
     /// Resolved config for web fetch.
     pub web_fetch_config: kigi_tools::implementations::grok_build::web_fetch::WebFetchConfig,
-    /// Image generation config (parent-inherited).
-    pub image_gen_config: kigi_tools::implementations::grok_build::image_gen::ImageGenConfig,
-    /// Resolved config for video generation.
-    pub video_gen_config: kigi_tools::implementations::grok_build::video_gen::VideoGenConfig,
     /// Resolved config for the deploy service.
     pub app_builder_deployer_config:
         kigi_tools::implementations::grok_build::deploy_app::AppBuilderDeployerConfig,
@@ -320,8 +315,6 @@ pub(crate) struct SubagentSpawnContext {
     /// time). Servers added later via `UpdateMcpServers` (managed MCPs, plugin reload)
     /// will not appear here. Named references only resolve against the initial config.
     pub parent_mcp_configs: Vec<agent_client_protocol::McpServer>,
-    /// Parent's managed MCP state handle (Arc-shared, no re-fetch).
-    pub managed_mcp_state: crate::session::managed_mcp::ManagedMcpStateHandle,
     /// Snapshot of the parent session's MCP client pool at spawn time.
     pub parent_mcp_pool: Option<crate::session::mcp_servers::SharedMcpPool>,
     /// Snapshot of the parent session's resolved tool schema at spawn time.