feat(delegate): add tiered subagent profiles

[MestreY0d4-Uninter]

Summary

This PR adds small, config-driven delegation tiers so subagents can use different model/reasoning/iteration profiles without forcing every task to share one flat delegation config.

This is a focused extraction from the larger delegation/credential-pool draft, but unlike the credential-pool slices it builds on the already separated reasoning-override work from #5337.

What changed

• add resolve_tier_config() in tools/delegate_tool.py
• support delegation.default_tier
• support delegation.tiers.<name> overrides
• add top-level tier to delegate_task
• add per-task tier in batch mode
• allow tier-specific overrides for:
  • model
  • provider
  • reasoning_effort
  • max_iterations
• add guardrails so heavier tiers do not silently degrade reasoning too far:
  • review / planning floor at high
  • heavy / research floor at medium

Why

Flat delegation config is too coarse once subagents start serving different roles.
A light worker, a deep review pass, and a planning agent often should not share the same model/reasoning settings.

This keeps the feature small and runtime-local:

• no new persistence layer
• no provider pool logic
• no retry/rate-limit changes
• no lease scheduling changes

Validation

Automated

• /home/ubuntu/.hermes/hermes-agent/venv/bin/python -m py_compile tools/delegate_tool.py hermes_cli/config.py tests/tools/test_delegate.py
• /home/ubuntu/.hermes/hermes-agent/venv/bin/python -m pytest -q -o addopts='' tests/tools/test_delegate.py -k 'DelegationReasoningEffort or TierResolution'
• Result: 8 passed, 51 deselected

Additional focused validation:

• /home/ubuntu/.hermes/hermes-agent/venv/bin/python -m pytest -q -o addopts='' tests/tools/test_delegate.py
• Result: 59 passed

Related context

• Builds logically on [DRAFT] fix(tools): support delegation reasoning overrides for subagents #5337 (fix(tools): support delegation reasoning overrides for subagents)
• Extracted from the larger draft: [DRAFT] fix(credential-pool): harden multi-account pool against rate limits and subagent stampede #5374
• Related issue: Feature: add named delegation capability profiles for subagents #4928 (named delegation capability profiles for subagents)
• Related PR thread: feat(delegation): add named subagent capability profiles #4929

Scope notes

This PR is intentionally limited to config-driven tier selection in delegation.
It does not add:

• credential-pool participation (fix(delegate): share credential pools with subagents #5576)
• lease-based child concurrency (fix(delegate): lease child pool credentials per task #5580)
• structured provider failure classification
• Retry-After parsing or fallback-precedence changes

[teknium1]

Closing — tiered subagent profiles add complexity we don't need right now. The flat delegation config is sufficient. Thanks for the clean implementation @MestreY0d4-Uninter.