Workflow panic when object schema is map during canvas type conversion

Describe the bug

Workflow test run may panic when object schema in canvas is encoded as map[string]interface{} instead of []interface{}.

Current panic:

Workflow execution failure: panic error: interface conversion: interface {} is map[string]interface {}, not []interface {}
.../backend/domain/workflow/internal/canvas/convert/type_convert.go:137

To Reproduce

Steps to reproduce the behavior:

1. Create or open a workflow containing LLM/object-related inputs/outputs.
2. Ensure one object schema is stored in map form (e.g. { "fieldA": {...}, "fieldB": {...} }) instead of array form.
3. Click test run (/api/workflow_api/test_run).
4. Backend panics during canvas schema conversion.

Expected behavior

Workflow execution should not panic. Canvas conversion should accept both object-schema representations (array and map) and return normal validation errors when input is invalid.

Screenshots

N/A (stack trace included above).

Version:

• branch: main (local reproduction)
• reproducible on current code before fix

Environment:

• go version go1.24.4 darwin/arm64
• GOOS=darwin
• GOARCH=arm64
• GOMOD=/Users/.../coze-studio/backend/go.mod

Additional context

Root cause is hard type assertion in type_convert.go assuming object schema is always []any. In practice, schema may come from map form after marshal/unmarshal or editor flow.

Proposed fix:

• normalize object schema to a common []any representation in conversion helpers
• support wrapped object schema ({"type":"object","schema":...})
• add tests for map-form schema and object-ref parsing
• avoid extra panic risk on filename metadata type assertion

Start at backend/domain/workflow/internal/canvas/convert/type_convert.go:137 and reproduce the panic through /api/workflow_api/test_run with a map-form object schema. Trace the conversion helpers, then add coverage for map-form schemas, wrapped object schemas, object-ref parsing, and filename metadata; done means both array and map forms avoid panics and invalid input returns validation errors.