Registry: POST /tasks accepts agent_name, loading <name>.json
from repo-root agents/ (traversal-guarded, skill-pack re-validated);
agent and agent_name together is a 400. Persistence: tasks gains
agent_name/agent_version/agent_instructions (migrate + PG schema),
returned by GET /tasks; stored prompt stays clean. Channel: local
and docker dispatch pass --developer-instructions to host.py
dispatch -> create_thread(developerInstructions=...); run/fork do
not re-send. Cloud executor has no such channel, so the worker
falls back to the v1 marked header in the in-memory dispatch
prompt only (DB prompt stays clean). Goal/coordinator tasks
still reject instructions.
Tests: test_agent_def_v2.py (7 tests) + updated v1 suite.
