resolve_agent_effort returned '' for all agents in prod because empty
ORCH_AGENT_EFFORT_*= env vars clobber pydantic class-defaults, leaving no
non-empty floor to fall back to -> --effort never reached the Claude CLI.
Add a level-4 per-role floor in resolve_agent_effort (src/agents/launcher.py):
_agent_effort_floor reads the declared class-default of agent_effort_<agent>
(model_fields[...].default), which a present-but-empty env cannot override.
Floor applies only when levels 1-3 are empty and BEFORE validation, so a typo
(non-empty) still drops to '' (never-break ORCH-41) and explicit env/override
still wins (priority preserved). config.py: agent_effort_developer high->xhigh
(single source of truth; floor follows automatically).
Refs: ORCH-081
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
