Runtime does not start workers for tools declared on a `planner=` agent

[ambiorix2099]

Files: src/conductor/ai/agents/runtime/runtime.py; reproduced by examples/agents/86_coding_agent.py

Symptom: python examples/agents/86_coding_agent.py hangs forever, no output after the worker banner. Output at 180s and 300s is byte-identical — no progress.

Cause: Workers start only for the parent agent's tools=. Tools declared on the agent passed as planner= get none, so the planner's read_file tasks stay SCHEDULED with nothing polling them. grep -n '\.planner' runtime.py matches only comments — no code reads that slot when collecting worker tools, while _ensure_models_for_agent walks a.agents recursively. Named slots planner=/fallback= replaced the older agents=[planner, fallback] form, which that traversal covered.

Fix: Collect worker tools through planner= and fallback=, not only agents=.

Verify: python examples/agents/86_coding_agent.py reaches the planner and stops hanging. Confirmed: supplying those four workers from a second process ends the hang (128s vs indefinite).

Note: This does not make 86 pass — it then fails with No JSON plan found and no fallback agent configured, a separate defect.

Also affects: 115_plan_execute_planner_context.py, adk/24_planner.py (4 examples use planner=, 8 use PLAN_EXECUTE).