Feature request: agentOverrides / agent listing budget, mirroring skillOverrides and skillListingBudgetFraction

Summary

Feature request: give the agent-type roster the same per-entry and total-budget controls that skills already have.

Skills have two effective cost controls today:

• skillOverrides per skill: "name-only", "user-invocable-only", "off"
• skillListingBudgetFraction (default 0.01) capping the listing's share of the context window, with automatic description shortening

Agents have neither. Every agent contributed by every enabled plugin is injected into the "Available agent types" listing in full (name + complete description, which for agent definitions is often several hundred characters each, sometimes with multi-example blocks). With agent-heavy plugin sets this is easily the single largest fixed context item.

Measured impact

With ~40 plugins enabled contributing 163 agent types, the roster measured ~56KB (~14k tokens at chars/4) per session — larger than the (budget-capped) skills listing — and it is paid again by each subagent that receives the listing.

Requested

Either or both of:

1. agentOverrides mirroring skillOverrides — per-agent "name-only" (listed without description; still spawnable) and "off" (unlisted; optionally still spawnable by exact name).
2. agentListingBudgetFraction mirroring skillListingBudgetFraction — a cap with automatic description truncation, so agent-heavy plugin sets degrade gracefully instead of growing without bound.

"name-only" alone would recover the majority of the cost while keeping every agent available, since descriptions dominate the bytes.

Environment

• Claude Code CLI (recent build, macOS/darwin)