scheduler: add 'none' scheduler_type to skip PodGroup creation

[jiaenren]

Summary

Implements Option C from #936: a new BackendSchedulerType.NONE that skips PodGroup CR creation and runs pods on the K8s default scheduler — removing the kai-scheduler hard dependency for workflows that don't need gang scheduling.

• BackendSchedulerType accepts 'none' in addition to 'kai'.
• get_k8s_object_factory() returns the base K8sObjectFactory(scheduler_name) for NONE. The base class already does what 'none' needs:
  • no PodGroup CR (just pods)
  • scheduler_name written to pod.spec.schedulerName
  • no scheduler resource CRDs (queues, topologies)
  • priority_supported / topology_supported return False
• openapi.json + UI generated types mirror the new enum value.

15 lines of code change across 5 files. The default behavior (scheduler_type='kai') is unchanged.

Test plan

OETF scenario test (in the internal harness, not part of this PR) exercises the path end-to-end on KIND:

1. POST /api/configs/backend/default with scheduler_type='none', scheduler_name='default-scheduler'.
2. Submit validation/workflow/serial_workflow.yaml.
3. Expect COMPLETED.
4. addCleanup restores the original backend config.

TDD verification on oetf:deploy --env kind --build-local:

Run	State	Result
pass-on-good	full Option C	PASS (workflow completes; no PodGroup CR is created)
fail-on-bad	enum + factory branch reverted	FAIL with 422 Input should be 'kai' (the exact symptom from #936)
pass-on-good (re-verify)	fix restored	PASS

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added support for a "none" backend scheduler option. When selected, pod scheduling uses the Kubernetes default scheduler instead of gang-scheduling, allowing for more flexible resource allocation configurations.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: d61d2377-dd6a-4c31-8d8a-d9ece1613272

📥 Commits

Reviewing files that changed from the base of the PR and between 01a90b5 and 3e3baa2.

📒 Files selected for processing (5)

• src/ui/openapi.json
• src/ui/src/lib/api/generated.ts
• src/ui/src/mocks/generated-mocks.ts
• src/utils/connectors/postgres.py
• src/utils/job/kb_objects.py

---

📝 Walkthrough

Walkthrough

This PR extends the backend scheduler type system from kai to include none. The change propagates through the OpenAPI schema, generated TypeScript client types, Python enum definition, and scheduler factory implementation to support Kubernetes scheduling without gang-scheduler/PodGroup features.

Changes

Add NONE scheduler type support

Layer / File(s)	Summary
API Contract src/ui/openapi.json	OpenAPI schema enum extends BackendSchedulerType to include "none" alongside "kai".
Generated Client Types src/ui/src/lib/api/generated.ts, src/ui/src/mocks/generated-mocks.ts	TypeScript generated API types and mock constants reflect the new none scheduler option in BackendSchedulerType.
Backend Scheduler Type Definition src/utils/connectors/postgres.py	Python BackendSchedulerType enum adds NONE = 'none' member with documentation explaining behavior without gang-scheduler/PodGroup creation.
Scheduler Factory Implementation src/utils/job/kb_objects.py	get_k8s_object_factory() adds explicit conditional branch for BackendSchedulerType.NONE to return base K8sObjectFactory with provided scheduler_name, replacing the prior unconditional error for unsupported scheduler types.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A scheduler type called "none" hops in,
No gang-gangs, no PodGroups—how light and slim!
Through schemas and types, the change does spring,
K8s default scheduling: the simplest thing! 🌿

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title accurately and concisely describes the main change: adding a 'none' scheduler type to skip PodGroup creation, which aligns with the core objective of supporting Kubernetes default scheduler without gang-scheduler dependencies.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch jiaenr/default-scheduler-exp

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.53%. Comparing base (01a90b5) to head (3e3baa2).

Files with missing lines	Patch %	Lines
src/utils/job/kb_objects.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #976      +/-   ##
==========================================
- Coverage   44.53%   44.53%   -0.01%     
==========================================
  Files         218      218              
  Lines       28537    28540       +3     
  Branches     4260     4261       +1     
==========================================
+ Hits        12708    12709       +1     
- Misses      15208    15210       +2     
  Partials      621      621              

Flag	Coverage Δ
backend	45.42% <25.00%> (-0.01%)	⬇️
ui	34.60% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/utils/connectors/postgres.py	71.50% <100.00%> (+0.01%)	⬆️
src/utils/job/kb_objects.py	77.95% <0.00%> (-0.85%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.