Add validation warnings to %choose magic for missing tasks/runs

[kaggle-agent]

When users run %choose with no tasks defined, they previously got
a confusing "run or evaluate" message. Now the magic distinguishes
between no tasks defined (links to @kbench.task docs) and tasks
defined but not run (links to .run()/.evaluate() docs). Warning
styling uses red text with code blocks at the same font size.

Co-authored-by: kaggle-agent [email protected]

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Task: psbang-20260410141748-045eace4
Context: https://chat.kaggle.net/kaggle/pl/da7aknogw7g5xr5yrj6ep4jr7e

[psbang]

@kaggle-agent this is completely wrong. The logic should live entirely in typescript/projects/kernel-editor/src/kernels/components/benchmarks/utils.tsx. Remember my instructions:

Just one small nit I noticed, if I have no tasks defined in the notebook I still get the new message saying I need to run or evaluate the task. Maybe if there are no tasks defined we could add a similar message that says "No tasks detected. Please create a task using the @kbench.task decorator". The kbench.task could link to this documentation: https://github.com/Kaggle/kaggle-benchmarks/blob/ci/user_guide.md#the-kbenchtask-decorator

We could also have the new message you wrote link to the documentation [here](https://github.com/Kaggle/kaggle-benchmarks/blob/ci/quick_start.md#basic-task) at the .run() or .evaluate() text block.

This should be a follow up to https://github.com/Kaggle/kaggleazure/pull/41465/changes. The "new message" I'm referring to is the message that starts with "Building a task requires benchmark results."

[kaggle-agent]

Re: @psbang's review:

You're right, I apologize. I've fully reverted the Python SDK changes (ipython_magics.py restored to original, test_choose_magic.py deleted) and moved the logic to typescript/projects/kernel-editor/src/kernels/components/benchmarks/utils.tsx as a follow-up to PR #41465.

Changes to utils.tsx:

1. No tasks detected (localTasks.length === 0): Added before the existing runTasks.length === 0 check. Displays "No tasks detected. Please create a task using the @kbench.task decorator" where @kbench.task is wrapped in TextLink → user_guide.md#the-kbenchtask-decorator and WarningCode for consistent font-size: 12px.

2. Doc links on .run() / .evaluate(): Wrapped the existing code blocks in TextLink components pointing to quick_start.md#basic-task.

3. Validation: Added localTasks.length === 0 → return false in validateBenchmarkTaskSelection.

All messages use the same WarningBody (red error color) + WarningCode (font-size: 12px) components as the existing "Can only save one task" warning.