chore: task completion tracking + workflow documentation

[patchmemory]

Summary

This PR adds the remaining task completion tracking and workflow documentation updates.

Changes Included:

1. Task Completion Tracking ✅

   • Marked 3 completed tasks as Done via dev_cli
   • Updated task frontmatter with completion timestamps
   • Committed dev submodule status updates

2. Workflow Documentation 📚

   • Updated dev/prompts.md with comprehensive task closure checklist
   • Added "Task Completion Checklist" section with 3 phases
   • Included example complete workflow from start to PR
   • Emphasized importance of dev_cli.py complete <task-id> step

Tasks Closed:

• task:interpreters/refactor/ipynb-streaming ✅
• task:interpreters/toggles/folder-config ✅
• task:ops/mvp/metrics-and-logs-endpoints ✅

Why This Matters:

Ensures proper task lifecycle management in the dev CLI system. Future work will have clear documentation on how to properly close out tasks.

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