Feature request: show context window usage percentage

Feature Request

Show a context window usage indicator (percentage or token count) in the Claude Code UI, similar to how Cursor and Codex display context usage.

Why

During long sessions that involve reading multiple files, PDFs, Slack messages, Jira API responses, and image analysis, it's hard to know how close you are to the context limit. The auto-compression happens silently and you only notice when Claude starts losing recall of earlier details.

A simple percentage indicator (e.g., "Context: 72%") in the status bar would help users:

• Know when to start a new session vs. continue
• Understand why certain details are being forgotten
• Plan how much more work they can do in the current session

Current Behavior

• No visibility into context usage
• Auto-compression happens silently when approaching limits
• Only way to check is to ask Claude "how's your context?"

Desired Behavior

• Persistent context usage indicator in the UI (percentage, token count, or progress bar)
• Visible in the status line or similar non-intrusive location

This would be especially useful for power users running long multi-tool sessions across Slack, Jira, GitHub, file reads, and PDF analysis.