fix(agent): hide retired issue-manager entry points

[rv4no]

Summary

• Add a host-owned AgentGUI switch to hide mention categories, including results tabs, keyboard cycling, and direct filter selection.
• Remove the retired Task Center home suggestion and prompt copy.
• Stop injecting the issue-manager skill and remove its AI routing guidance from runtime preparation.
• Preserve legacy issue mention parsing/rendering and the advertised issue CLI command data for existing content and explicit CLI use.

Tests

• pnpm --dir packages/agent/gui test -- --run
• pnpm --dir packages/agent/gui typecheck
• go test ./packages/agent/runtimeprep

Notes

• This is the upstream tutti-os/tutti change. TSH package version updates remain pending until the upstream packages are published.
• No platform-specific runtime primitives or filesystem behavior changed.