add resume method and refactor

[a-fatah]

Adds missing resume mutation in journal.ts and method in workflow manager client and other improvements:

1. Schema Changes (schema.ts)

• introduces a discriminated union ExecutionStep | PauseStep
• Each step has a type field execution or pause
• Execution steps now only have functionType (query/mutation/action) and handle meaning 'pause' is no longer modeled as an execution type
• Pause steps have optional onPauseHandle

2. Step Request Types split into ExecutionStepRequest and PauseStepRequest (step.ts)

3. Step Context (stepContext.ts)

   • Refactored pause() to use PauseStepRequest
   • Removed polluted FunctionType | "pause" types
   • Clean separation of execution and pause logic

4. Journal Handler (journal.ts)

   • Updated to handle discriminated union
   • Clean type narrowing with step.type === "execution"
   • Changed pause filter from functionType === "pause" to type === "pause"

5. Pool Handler (pool.ts)

   • Updated pause detection to use step.type === "pause"

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