feat(workflow): add MDL syntax for outcome parameter mappings in CALL MICROFLOW / CALL WORKFLOW

[engalar]

Summary

CALL MICROFLOW and CALL WORKFLOW activities support parameter mappings in BSON (the executor auto-binds $WorkflowContext for call-workflow), but MDL has no syntax for users to specify explicit parameter values. This limits the expressiveness of workflow scripts.

Gap

Layer	Status
BSON Parser	✅ Fully implemented
BSON Writer	✅ Implemented (auto-bind only)
MDL Grammar	❌ No WITH / PARAMETERS clause
MDL Executor	❌ No explicit parameter handler

Key Files & Lines

BSON Writer — where auto-binding happens (extend to accept explicit mappings)

• sdk/mpr/writer_workflow.go:412-426 — ParameterMappings for CallMicroflowTask; array marker int32(2)
• sdk/mpr/writer_workflow.go:464-478 — ParameterMappings for CallWorkflowActivity; array marker int32(2)

BSON Parser — already implemented, reference only

• sdk/mpr/parser_workflow.go:354-355 — parseBoundaryEvents call site (adjacent to where parameter mappings are parsed)

Grammar — where to add syntax

• mdl/grammar/MDLParser.g4:2247-2254 — workflowCallMicroflowStmt and workflowCallWorkflowStmt; add optional WITH (param = expr, ...) clause

Executor — where to wire up

• mdl/executor/cmd_workflows_write.go:159-194 — buildWorkflowActivities()

AST — where to add fields

• mdl/ast/ — extend WorkflowCallMicroflowNode and WorkflowCallWorkflowNode with Parameters []WorkflowParamMapping

Proposed MDL Syntax

CALL MICROFLOW MyModule.CalculateDiscount
  WITH (OrderAmount = '$WorkflowContext/TotalAmount', CustomerId = '$WorkflowContext/CustomerId')
  OUTCOMES 'Approved' -> { } 'Rejected' -> { };

CALL WORKFLOW MyModule.SubApprovalWorkflow
  WITH (Context = '$WorkflowContext');

Notes

• $WorkflowContext auto-binding for CALL WORKFLOW can remain the default when no WITH clause is given
• Parameter types must match the microflow/workflow parameter types (expression vs object reference)
• Array marker for ParameterMappings is always int32(2) — see writer_workflow.go:413