feat: add workflow runner with per-step retry support

[yohaiai]

Summary

• Adds workflow-runner.ts — a multi-step workflow orchestrator with configurable per-step retry support
• Each WorkflowStep can specify a retries count (default 0 = no retry, backwards compatible)
• On retry, the step's app is re-launched for fresh state — critical for time-sensitive operations like TOTP 2FA where the 30-second code window may expire during execution
• Emits workflow_step_retry dashboard events for retry visibility

Motivation

When automating flows like Instagram login with Chrome-based TOTP 2FA, the 6-digit code rotates every 30 seconds. If the code expires mid-step, the step fails. With retries: 4, we get ~5 attempts to hit a valid window, making success highly likely.

Usage

{
  "app": "com.android.chrome",
  "goal": "Copy TOTP code from Chrome, switch to Instagram, paste and submit",
  "maxSteps": 15,
  "retries": 4
}

Steps without retries behave exactly as before (single attempt, fail immediately on error).

Test plan

• Verify steps without retries field work identically to current behavior
• Verify step with retries: N retries up to N times on failure
• Verify app is re-launched on each retry attempt
• Verify workflow_step_retry dashboard events are emitted with correct attempt/maxRetries
• Verify successful retry breaks out and continues to next step
• Verify exhausted retries marks workflow as failed

Note: This file requires the workflowRun schema table to be added to schema.ts (not included in this PR as it depends on your schema setup).

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