Expose aggregate submission queue status

[msaroufim]

Summary

Adds aggregate submission queue metadata to KernelBot background submissions without exposing other users' identities or submission IDs.

The API now returns a queue object on submission acceptance and on user submission polling. It includes the caller's position, jobs ahead, pending/running counts, worker counts, and a flag clarifying that external runner queues are not visible.

Why

Users can see whether they are waiting in KernelBot's in-process queue versus waiting on runner execution, while avoiding disclosure of who else is queued.

Validation

• uv run --with pytest --with pytest-asyncio pytest tests/test_background_submission_manager.py tests/test_admin_api.py

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
src/libkernelbot
background_submission_manager.py
utils.py
Project Total

This report was generated by python-coverage-comment-action

[msaroufim]

Additional local e2e validation after opening the PR:

• Ran a local FastAPI KernelBot harness on 127.0.0.1:8766 using the real BackgroundSubmissionManager and a fake runner/DB.
• Preloaded one pending job, held workers at 0, submitted a second job through the actual popcorn-cli binary over HTTP, then released workers.
• CLI output included:

Submission 1001 accepted (kernelbot queue position 2, 1 ahead; 2 pending, 0 running, workers 0/0; runner queue not visible). Waiting for results...
Submission 1001 status: pending (kernelbot queue position 2, 1 ahead; 2 pending, 0 running, workers 0/0; runner queue not visible, 0s)
Submission 1001 status: pending (kernelbot queue position 2, 1 ahead; 2 pending, 0 running, workers 0/0; runner queue not visible, 5s)
Submission 1001 status: succeeded (kernelbot queue: 0 pending, 0 running, workers 2/2; runner queue not visible, 10s)

This verifies the API response shape and CLI display path end to end without invoking Modal/GitHub.

[msaroufim]

Updated after simplifying the queue status shape.

Local e2e validation with a real HTTP path still passes:

• Ran a local FastAPI KernelBot harness on 127.0.0.1:8766 using the real BackgroundSubmissionManager and a fake runner/DB.
• Preloaded one pending job, held workers at 0, submitted a second job through the actual popcorn-cli binary over HTTP, then released workers.
• CLI output now uses the simplified messages:

Submission 1001 accepted: In KernelBot queue (position 2, 1 ahead). Waiting for results...
Submission 1001 status: pending - In KernelBot queue (position 2, 1 ahead) (0s)
Submission 1001 status: succeeded - Job dispatched to Modal/GitHub runner (5s)

The public queue payload is now limited to stage, message, and optional position / jobs_ahead.

[msaroufim]

Closing this draft; queue-position metadata does not answer the more useful wait-time/debugging question.