Feature: /context output should show summary at bottom, not top

Problem

When running /context, the most important information (token usage summary) appears at the TOP of a very long output. The majority of the output is a detailed breakdown of MCP tools, memory files, and skills — which scrolls the summary off-screen.

Users have to scroll UP past ~200 lines of tool/skill listings to see the actual usage numbers they care about.

Suggestion

Show the summary section at the BOTTOM of the output (or at both top and bottom), so the user sees it immediately without scrolling:

[... detailed MCP tools, skills, memory files ...]

## Context Usage Summary
Model: claude-opus-4-6[1m]
Tokens: 589.6k / 1m (59%)
Free space: 344.3k (34.4%)

Alternatively, add a /context --brief flag that shows only the summary table without the detailed breakdowns.

Context

In long sessions (50%+ context used), checking remaining capacity is a frequent action. Having to scroll past tool listings every time is friction that adds up.