[FEATURE]: Allow configurable subagent-to-subagent task delegation with call limits

[NamedIdentity]

Feature hasn't been suggested before.

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Describe the enhancement you want to request

Problem Currently, task.ts hardcodes task: false for all subagent sessions (lines 65-69, 132-137), preventing any subagent from delegating to another subagent. This blocks legitimate workflows like:

• Principal-Partner delegating to Assistants
• Assistant-Sonnet having Assistant-Flash cross-check its work
• Assistant-Flash asking Assistant-Sonnet for thorough analysis

The agent config already supports granular task permissions:

assistant-sonnet: { tools: { task: true }, permission: { task: { *: deny, assistant-flash: allow } } }

But this config is ignored because task.ts unconditionally overrides it.

Proposed Solution

1. Respect agent-level task permissions instead of hardcoding task: false
2. Add optional task_limit config to prevent infinite loops: assistant-sonnet: { tools: { task: true }, permission: { task: { *: deny, assistant-flash: allow } }, task_limit: 3 // Max task calls per session (0 = current behavior) }

Use Case Building an Agentic Collaboration Framework where:

• Principal-Opus orchestrates work
• Principal-Partner (subagent) can delegate to Assistants
• Assistant-Sonnet and Assistant-Flash can cross-check each other's work

The permission system already expresses "Sonnet can only task Flash" - it just needs to be honored.

Backward Compatibility Default behavior unchanged - task_limit: 0 (or absent) means task tool disabled for subagents, matching current behavior. Only users who explicitly configure permissions get the new capability.