[TUI] Effort level indicator flickers — should be persistent or hideable

Problem

The native effort level indicator (● high · /eff…) in the TUI appears and disappears inconsistently. An indicator that comes and goes is worse than no indicator at all — it creates visual noise without being reliably informative.

Expected Behavior

Either:

1. Stay visible persistently when effort level is set, or
2. Be hideable via a settings.json toggle (e.g. "showEffortIndicator": false)

Workaround

I display effort level in a custom statusline by reading effortLevel from ~/.claude/settings.json directly. This works but is a workaround — the proper fix would be to expose effortLevel in the statusline JSON payload (as requested in #42358, #41049, #38392, #37764, #36187, #31415) so custom statuslines can display it from a single source of truth without file I/O on every update.

Context

• The VS Code extension has the same complaint: #33667
• UI reflection of effort level has been reported as inaccurate: #31751
• Multiple issues request effortLevel in statusline JSON — this is the most-requested statusline field

Environment

• Platform: macOS (darwin)
• Terminal: TUI
• Custom statusline: bash script reading from stdin JSON