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/util/config/mcp.rs

@@ -328,12 +328,10 @@ pub fn all_toml_mcp_server_names(cwd: &std::path::Path) -> std::collections::Has
     load_all_mcp_configs(cwd).keys().cloned().collect()
 }
 
-pub const MANAGED_GATEWAY_DISABLED_CONNECTORS_KEY: &str = "__managed_gateway_connectors";
-
 /// Persist `disabled_tools` for a server under `[disabled_mcp_tools]` in config.toml.
 ///
 /// Uses a dedicated top-level section (not `[mcp_servers]`) to avoid creating
-/// incomplete server entries that fail to deserialize for managed servers.
+/// incomplete server entries that fail to deserialize.
 pub async fn save_mcp_disabled_tools(server_name: &str, disabled_tools: &[String]) -> Result<()> {
     let path = config_path();
     let mut root: TomlValue = match tokio::fs::read_to_string(&path).await {