Add disk eject button and network speed color indicator

[ysyyork]

Summary

• Add eject button for non-root disks (external drives, network disks)
• Show green color for network speeds > 1MB/s in menu bar
• Update NetworkContentView dropdown to also show green for fast speeds
• Add tests for eject eligibility and speed color threshold

Test plan

• Verify eject button appears for external drives and network disks
• Verify eject button does NOT appear for root volume (Macintosh HD)
• Verify network speed turns green when > 1MB/s
• Verify network speed is white/normal when ≤ 1MB/s
• Run tests to verify new test cases pass

🤖 Generated with Claude Code

[ysyyork]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

🤖 Generated with Claude Code

_{- If this code review was useful, please react with 👍. Otherwise, react with 👎.}