[Feature Request] Add --summary flag to /context command for token usage only

Bug Description
Title: Feature request: Add --summary or --terse flag to /context command

Description:

The /context command outputs detailed information about all MCP tools, memory files, and skills, which causes the summary line (token usage) to scroll off the screen in normal terminal windows.

Problem:

• The most useful information (e.g., 98k/200k tokens (49%)) appears at the top
• Detailed breakdowns of MCP tools (~28 items), memory files, and skills (~18 items) push this off-screen
• Users wanting a quick token check must scroll back up

Requested solution:
Add a flag like /context --summary or /context --terse that outputs only:
claude-opus-4-5-20251101 · 98k/200k tokens (49%)

Or a compact version showing just the category totals without individual item breakdowns:
98k/200k (49%) | System: 19.5k | MCP: 18.3k | Memory: 9.5k | Messages: 5.7k | Free: 102k

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.0.75
• Feedback ID: 573e8565-21b5-44bf-8bcc-b4d0d9674043

Errors

[{"error":"Error: Request was aborted.\n    at _createMessage (/$bunfs/root/claude:458:3157)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-22T07:24:14.997Z"},{"error":"Error: Request was aborted.\n    at _createMessage (/$bunfs/root/claude:458:3157)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-22T07:24:24.785Z"}]