refactor(frontend): extract Data Card and Versions & Files tabs

[rbelavadi]

What changes were proposed in this PR?

Extracts the remaining content on the dataset detail page into two new tabs: Data Card and Versions & Files. Part of #6394; second of two sub-issues (#6395, Settings, already merged).

• Versions & Files: pure relocation. The existing file browser, version selector, file preview, and upload widget move here unchanged.
• Data Card: new read-only overview, two cards:
  • Description (moved out of the page header, which previously duplicated it, the header now shows name/badges/counts only), using the existing texera-markdown-description component's built-in "View more" collapse for long descriptions.
  • Key facts panel: Created date, Last updated (latest version's creation date, independent of whatever's selected in Versions & Files), Latest version file name, Latest version size, and Versions count.

Before: two tabs- Data Card (holding everything: file browser, version history, uploads, plus a duplicated description in the header) and Settings.

After: three tabs- Data Card (read-only overview only), Versions & Files (file/version management, split out of the old Data
Card tab), and Settings (unchanged).

Any related issues, documentation, discussions?

Closes #6942

How was this PR tested?

Added 7 unit tests to dataset-detail.component.spec.ts covering the new Data Card logic:

• "Last updated" derives from the latest version, independent of whichever version is selected in Versions & Files.
• retrieveLatestVersionFile() correctly resolves the latest version's file name, including nested paths and the no-files case.
• Selecting a version with an empty file tree no longer throws.

Manually tested on UI:

• Versions & Files retains all existing functionality (file browsing, version switching, file preview, upload) unchanged.
• Description renders correctly in Data Card, including markdown formatting and the "View more" collapse on long descriptions.
• Settings tab (merged separately in Refactor dataset detail page: extract Settings tab #6395) is unaffected.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Opus 4.8)

[github-actions]

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[rbelavadi]

/request-review @xuang7

[codecov-commenter]

Codecov Report

❌ Patch coverage is 68.39623% with 67 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.60%. Comparing base (421e660) to head (2f28ccd).

Files with missing lines	Patch %	Lines
...ser-dataset-explorer/dataset-detail.component.html	64.36%	66 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7043      +/-   ##
============================================
+ Coverage     79.57%   79.60%   +0.03%     
- Complexity     3832     3836       +4     
============================================
  Files          1159     1159              
  Lines         46122    46162      +40     
  Branches       5127     5133       +6     
============================================
+ Hits          36700    36747      +47     
+ Misses         7790     7787       -3     
+ Partials       1632     1628       -4     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from d0c6441
agent-service	77.42% <ø> (ø)		Carriedforward from d0c6441
amber	73.11% <ø> (+0.04%)	⬆️	Carriedforward from d0c6441
computing-unit-managing-service	20.49% <ø> (ø)		Carriedforward from d0c6441
config-service	66.66% <ø> (ø)		Carriedforward from d0c6441
file-service	67.21% <ø> (ø)		Carriedforward from d0c6441
frontend	83.08% <68.39%> (+0.02%)	⬆️
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from d0c6441
pyamber	97.36% <ø> (ø)		Carriedforward from d0c6441
workflow-compiling-service	26.31% <ø> (ø)		Carriedforward from d0c6441

*This pull request uses carry forward flags. Click here to find out more.

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[xuang7]

Thanks for the PR! It generally looks good to me. I left a few minor comments. Please also try to improve the test coverage.

[Copilot]

Pull request overview

Refactors the Angular dataset detail page in the frontend dashboard by splitting responsibilities across tabs, aiming to reduce clutter and separate read-only dataset metadata from file/version management workflows.

Changes:

• Introduces a read-only Data Card tab that surfaces dataset description and key facts.
• Moves the existing file browser/version selector/upload UI into a new Versions & Files tab.
• Adds component logic + unit tests to derive “latest version” facts independently from the currently selected version.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
frontend/src/app/dashboard/component/user/user-dataset/user-dataset-explorer/dataset-detail.component.ts	Adds latest-version state and retrieval logic; hardens file-tree selection against empty trees.
frontend/src/app/dashboard/component/user/user-dataset/user-dataset-explorer/dataset-detail.component.html	Splits UI into Data Card vs Versions & Files tab content; adjusts Settings hint text.
frontend/src/app/dashboard/component/user/user-dataset/user-dataset-explorer/dataset-detail.component.scss	Adds layout and scrolling styles for the new tab contents and Data Card cards.
frontend/src/app/dashboard/component/user/user-dataset/user-dataset-explorer/dataset-detail.component.spec.ts	Adds/updates unit tests for Data Card latest-version behavior and tab-rendering implications.

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[xuang7]

LGTM!