Add --compact flag to /context to collapse MCP tool list

Problem

When running /context, the MCP tools section enumerates every available tool individually. With MCP servers that expose many tools (e.g., the official Atlassian MCP exposes ~30 tools), the list pushes the actual token usage breakdown off the top of the terminal. Users have to scroll back up to see the numbers they opened /context for.

Proposed solution

Add a --compact (or similar) flag to /context that collapses verbose sections:

• MCP tools: show per-server tool counts instead of listing every tool (similar to what /mcp already does)
• Custom agents, Skills, Memory files: optionally collapse to counts + total tokens

Example compact output for the MCP section:

MCP tools · /mcp (loaded on-demand)
├ atlassian: 31 tools
└ (other servers...)

Why this helps

The primary reason to run /context is to see the token usage breakdown. The detailed tool enumeration is useful occasionally (debugging why something isn't loaded), but not on every invocation. A compact mode would make /context much faster to scan during normal work.

Workarounds today

• /mcp shows server-level tool counts without full enumeration
• Scroll to the top of the output manually