Type eventParams (behaviors + automations) — fill AutomationEventParamsInput

[mocha06]

Part of the "Typed payloads: parse, don't validate" milestone. Follows #416 / PR #417.

Problem

eventParams is walked with dual-alias branches in several places instead of a typed model:

• ai_pipe_validation.py: ep.get("to_phase_id") or ep.get("toPhaseId")
• ai_phase_transition_validation.py: src = ep.get("to_phase_id") or ep.get("toPhaseId")
• automation_preflight.py: extra.get("event_params") or extra.get("eventParams"), then ev.get("to_phase_id") or ev.get("toPhaseId")

AutomationEventParamsInput already exists as an empty-shell pydantic model (models/ai_automation.py, extra="allow", no fields), so event_params on behaviors/automations is effectively untyped.

Wire shape (introspected, dev)

AutomationEventParamsInput inputFields: kindOfSla, fromPhaseId, inPhaseId, to_phase_id (snake!), triggerAutomationId, triggerFieldIds.

Note the mixed casing in one type: to_phase_id is snake while its siblings are camel — per-declared-field aliases only, never a blanket converter.

Scope

• Fill AutomationEventParamsInput with the six declared fields (populate_by_name=True, per-field aliases, keep extra="allow").
• Type event_params on the behavior read/normalize path (BehaviorPayload, BehaviorInput) and the automation input, and read typed attributes at the consumers above.
• Delete the to_phase_id/toPhaseId and event_params/eventParams dual-alias branches.

Sequencing

Touches models/ai_agent.py and models/ai_automation.py. Sequence after #410 (capability/provider hardening) to avoid conflicts on models/ai_agent.py.

Acceptance

• No to_phase_id/toPhaseId or event_params/eventParams dual-alias branches remain in the migrated paths.
• uv run pytest -m "not integration" + ruff + import-linter green.