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).

Cargo.toml

@@ -44,7 +44,6 @@ members = [
     "crates/codegen/kigi-shared",
     "crates/codegen/kigi-shell",
     "crates/codegen/kigi-shell-base",
-    "crates/codegen/kigi-shell-session-support",
     "crates/codegen/kigi-subagent-resolution",
     "crates/codegen/kigi-test-support",
     "crates/codegen/kigi-tools",
@@ -274,7 +273,6 @@ kigi-secrets = { path = "crates/codegen/kigi-secrets" }
 kigi-shared = { path = "crates/codegen/kigi-shared" }
 kigi-shell = { path = "crates/codegen/kigi-shell" }
 kigi-shell-base = { path = "crates/codegen/kigi-shell-base" }
-kigi-shell-session-support = { path = "crates/codegen/kigi-shell-session-support" }
 kigi-log = { path = "crates/codegen/kigi-log" }
 kigi-test-support = { path = "crates/codegen/kigi-test-support" }
 kigi-tools = { path = "crates/codegen/kigi-tools" }