feat(swarm): add slash-command swarm mode and provider-native roles

[boggedbrush]

Summary

This adds a new /swarm workflow for Kodo Code that replaces the standard Ask, Plan, Code, and Review mode buttons with a slash-command-driven swarm state.

When enabled, swarm drives work through explicit Questionnaire, Planner, Coder, and Reviewer roles, with a configurable loop cap of one or two passes.

What Changed

• Added swarm as a provider interaction mode and introduced a shared swarmMaxLoops setting capped to 1 | 2.
• Changed the web UX so /swarm toggles swarm on and off, the mode pill collapses to a single Swarm indicator, and the standard mode controls are hidden while swarm is active.
• Kept the standard circular send button while swarm is enabled.
• Added shared swarm copy for the active state in the composer UI.
• Added server-side swarm orchestration helpers and loop-cap normalization.
• Wired Codex swarm to stronger collaboration instructions that require real delegated Questionnaire, Planner, Coder, and Reviewer roles when native collaboration tools are available.
• Wired Claude swarm to real SDK-defined subagents for those four roles using provider-native agents definitions.
• Added and updated targeted tests for slash command parsing, loop-cap propagation, swarm UI state, and provider swarm behavior.

Why

The goal is to remove guesswork for long-running coding tasks by making role separation explicit and repeatable instead of relying on a single agent to improvise analysis, planning, implementation, and review in one pass.

User Impact

• Users can toggle swarm with /swarm.
• Swarm no longer appears as a regular mode button alongside Ask, Plan, Code, and Review.
• While active, swarm presents itself as a dedicated workflow instead of a normal mode.
• Claude now gets real swarm subagents, and Codex gets stricter multi-agent collaboration guidance.

Validation

• git diff --check
• bun fmt could not be run in this environment because bun is unavailable.
• bun lint could not be run in this environment because bun is unavailable.
• bun typecheck could not be run in this environment because bun is unavailable.

Screenshot