Type classic automation params in automation_preflight

[mocha06]

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

Problem

Classic (non-AI) automation preflight walks CreateAutomationInput-style dicts with dual-alias branches in automation_preflight.py:

• extra.get("event_params") or extra.get("eventParams"), ev.get("to_phase_id") or ev.get("toPhaseId")
• extra.get("action_params") or extra.get("actionParams"), act.get("to_phase_id") or act.get("toPhaseId")
• act.get("field_map") or act.get("fieldMap"), entry.get("fieldId") or entry.get("field_id")

Wire shape (introspected, dev)

• CreateAutomationInput: action_id, event_id, action_params (→ AutomationActionParamsInput), event_params (→ AutomationEventParamsInput), condition, name, ... — snake_case input field names.
• AutomationActionParamsInput: field_map (snake) alongside aiBehaviorParams/httpMethod (camel), plus card_id, email_template_id, to_phase_id, fields_map_order (snake).
• FieldMapInput: fieldId, inputMode, value (camel; fieldId/inputMode NON_NULL).

Live proof (dev, createAutomation) — the second spelling never worked

• action_params.field_map[0].field_id (snake) → Field is not defined on FieldMapInput.
• action_params.field_map[0].fieldId (camel) → passes coercion.
• action_params.fieldMap (camel wrapper) → Field is not defined on AutomationActionParamsInput.

So fieldMap and field_id in the dual-alias branches accept inputs the API always rejected.

Scope

• Model the classic-automation params subtree (AutomationActionParamsInput fields the preflight touches: field_map, to_phase_id, phase) with per-declared-field aliases, extra="allow", reusing the shared FieldMapInput model from the behavior-metadata issue.
• Read typed attributes in automation_preflight.py; delete the dual-alias branches. Update any tests pinning the (non-functional) camel/snake passthrough to the declared names.

Acceptance

• No dual-alias branches remain in automation_preflight.py.
• uv run pytest -m "not integration" + ruff + import-linter green.