feat(studio): Data sample panel

[steramae-nvidia]

This PR adds a data sample to the bottom right panel in order to support quick previews of the data in the dataset card case.

This also slightly changes the panel layout in the FilesetCard component. It adds a Resizeable panel so users can choose which view to focus on (README or the dataset sample)

Summary by CodeRabbit

• New Features

  • Data sample preview panel for dataset filesets with file selection, sampling method, and row-count controls.
  • Resizable two-pane layout for improved content organization.

• Bug Fixes

  • Parquet BigInt values now serialize safely as strings for downloads/previews.

• Improvements

  • Centered loading spinner during file fetches and inline error banners on load failure.
  • Added a loading scenario to component previews.

• Tests

  • New tests for sampling panel and file-content handling.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 03dc6f1 and 0fe3218.

📒 Files selected for processing (1)

• web/packages/studio/src/routes/FilesetDetailRoute/FilesetCard/DatasetSamplePanel.tsx

🚧 Files skipped from review as they are similar to previous changes (1)

• web/packages/studio/src/routes/FilesetDetailRoute/FilesetCard/DatasetSamplePanel.tsx

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📝 Walkthrough

Walkthrough

Adds BigInt-safe Parquet row serialization; shows a centered Spinner and early-error Banner in FileSamplingSnippet; adds DatasetSamplePanel with tests; integrates the panel into FilesetCard using ResizeablePanel; and tweaks route/container sizing and a test assertion.

Changes

Dataset file preview and sampling

Layer / File(s)	Summary
Parquet BigInt safe serialization web/packages/studio/src/api/datasets/useDatasetFileContent.ts, web/packages/studio/src/api/datasets/useDatasetFileContent.spec.ts	Adds jsonReplacer and serializeParquetRow to convert bigint values to strings when serializing Parquet rows; replaces direct JSON.stringify usage and adds tests verifying JSONL output contains stringified BigInt.
FileSamplingSnippet loading and error UI web/packages/studio/src/components/FileSamplingSnippet/FileSamplingSnippet.tsx, web/packages/studio/src/components/FileSamplingSnippet/FileSamplingSnippet.stories.tsx	Imports Flex/Spinner, shows a centered Spinner while file content loads, standardizes the empty-state message, removes requestStatus prop, returns an inline Banner on load error, and adds a Loading Story with delayed MSW handlers.
DatasetSamplePanel component and tests web/packages/studio/src/routes/FilesetDetailRoute/FilesetCard/DatasetSamplePanel.tsx, web/packages/studio/src/routes/FilesetDetailRoute/FilesetCard/DatasetSamplePanel.spec.tsx	New component for data sampling with file selection, sampling method and max-row controls, and display-mode heuristics; tests cover empty state, defaults, file listing, mode selection, file switching, and method selection.
FilesetCard layout and DatasetSamplePanel integration web/packages/studio/src/routes/FilesetDetailRoute/FilesetCard/index.tsx	Replaces Grid layout with ResizeablePanel and conditionally renders DatasetSamplePanel when fileset.purpose === FilesetPurpose.dataset; updates imports.
Container sizing and scroll behavior adjustments web/packages/studio/src/components/common/ResizeablePanel/index.tsx, web/packages/studio/src/routes/FilesetDetailRoute/index.tsx	Adds w-full to ResizeablePanel wrapper; simplifies FilesetDetailRoute sizing and removes prior flex/overflow utilities from TabsContent.
Test assertion updates web/packages/studio/src/components/evaluation/Jobs/form/MetricTestPanel.spec.tsx	Replaces an empty-editor assertion with an explicit "Failed to load file content..." error message assertion while keeping "Run Test" disabled expectation.

Possibly related PRs

• NVIDIA-NeMo/nemo-platform#166: Related FilesetCard UI composition work.

Suggested reviewers

• htolentino-nvidia
• nv-odrulea

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% 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	Title accurately summarizes the main addition: a new data sample panel component for dataset preview functionality in the FilesetCard.
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.

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✨ 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 steramae/astd-174-filesets-dataset-preview-on-card-tab

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[github-actions]

Suite	Lines Covered	Line Rate	Branch Rate
Unit Tests	18712/24765	75.6%	62.0%
Integration Tests	11992/23529	51.0%	26.1%

[htolentino-nvidia]

I like the idea a lot, I'm just getting a bit of a weird behaviour with the scrolling on that section:

[steramae-nvidia]

I like the idea a lot, I'm just getting a bit of a weird behaviour with the scrolling on that section:

@htolentino-nvidia taking a look!

[steramae-nvidia]

I like the idea a lot, I'm just getting a bit of a weird behaviour with the scrolling on that section:

@htolentino-nvidia taking a look!

Fixed by removing one scroll bar on the outer container (the inner data view still needs scroll bars)