[FEATURE] Toggleable columns in agent view: model, effort, and context usage

Preflight Checklist

• [x] Searched existing requests — closest are #24537 (subagent hierarchy dashboard) and #44723 (peak context in result JSON); neither targets the new claude agents view rows.
• [x] This is a single feature request.

Problem Statement

The agent view (claude agents, v2.1.139 Research Preview) lists background sessions with a state icon, name, activity summary, last-changed time, and PR dot. When you're running several parallel sessions, three things you most need to triage are not visible per row:

• Which model each session is on — the header shows only the dispatch default; per-session --model / /model overrides are invisible.
• Reasoning effort — sessions dispatched with different --effort (low/medium/high) look identical.
• Context fill — there's no way to see which session is near compaction without attaching to it.

Today you have to attach to each session one by one to answer "which one is the expensive Opus/high-effort run, and which is about to compact?"

Proposed Solution

Add three optional columns to the agent view table, off by default, toggled via a keybind (mirroring the existing Ctrl+S regroup-by-directory affordance):

| Column | Content | Example |
|--------|---------|---------|
| Model | Effective model of the session | opus-4-7 / sonnet-4-6 |
| Effort | The --effort setting | high / med / low |
| Context | Used / max tokens and percentage | 142K/200K (71%) |

The Context column should color-grade (e.g. yellow >70%, red >90%) so a near-compaction session is obvious at a glance.

Keep it opt-in so the default view stays terse — a footer hint (e.g. Ctrl+L: columns) and persistence of the toggle in /config would match existing patterns.

Rationale

Triaging parallel sessions is the core job of agent view. Model and effort drive cost; context fill drives when a session needs a /compact or hand-off. All three are already known to the supervisor process — this is a display gap, not new instrumentation. Keeping the columns toggleable respects the width-constrained row design.

Priority

Medium — High for users running 3+ parallel background sessions.

Feature Category

TUI / agent view

Use Case Example

Five background sessions running. With columns enabled, the user instantly sees session B is opus-4-7 / high / 188K/200K (94%) in red — they attach and /compact it before it auto-compacts mid-task, and notice session D is needlessly on opus / high for a trivial docs edit.

Suggested Labels

enhancement, area:agent-view