feat: Add tasks for S8PC #4 (#3264)

[KATO-Hiro]

close #3264

Summary by CodeRabbit

• New Features

  • Added support for square869120Contest 4 with a new problem "Driving on a Tree."
  • Updated contest name resolution to recognize the new contest designation.

• Tests

  • Added test cases for the new contest and problem registration.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 8e9bcc7e-99f7-4e9b-a190-d3b28e746721

📥 Commits

Reviewing files that changed from the base of the PR and between 7f225f7 and 0bb07aa.

📒 Files selected for processing (5)

• docs/dev-notes/2026-03-14/add-rerooting-dp-to-contests/plan.md
• prisma/tasks.ts
• src/lib/utils/contest.ts
• src/test/lib/utils/test_cases/contest_name_labels.ts
• src/test/lib/utils/test_cases/contest_type.ts

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Walkthrough

This PR adds support for the s8pc-4 AtCoder contest (square869120Contest #4) by registering it in contest utilities, adding a new "Driving on a Tree" task to the dataset, and including corresponding test cases to validate the changes.

Changes

Cohort / File(s)	Summary
Contest Registration & Utilities src/lib/utils/contest.ts	Added s8pc-4 to ATCODER_OTHERS constant mapped to 'square869120Contest #4'. Modified getContestNameLabel to include an early lookup in ATCODER_OTHERS before other fallback handling.
Task Data prisma/tasks.ts	Added new task entry for s8pc_4_d ("Driving on a Tree") with contest_id 's8pc-4' and problem_index 'D'.
Test Cases src/test/lib/utils/test_cases/contest_type.ts, src/test/lib/utils/test_cases/contest_name_labels.ts	Added test case entries validating that contest 's8pc-4' is correctly classified as ContestType.OTHERS and returns label 'square869120Contest #4'.
Documentation docs/dev-notes/2026-03-14/add-rerooting-dp-to-contests/plan.md	Added development notes documenting the addition of the s8pc-4 contest, new task, test cases, and refactoring guidance for generalizing contest classification via handler-based approach.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A tree to drive upon we add,
With s8pc-4 contest so glad,
Rerooting logic now takes the stage,
Square's challenge marks another page,
From AtCoder's garden, fresh and bright! 🌳

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: Add tasks for S8PC #4' accurately describes the main change—adding new tasks for the S8PC #4 contest, which aligns with the changeset.
Linked Issues check	✅ Passed	The PR successfully implements the coding requirement from issue #3264 by adding the 's8pc_4_d' task (Driving on a Tree) from S8PC #4 with proper contest configuration.
Out of Scope Changes check	✅ Passed	All changes are directly related to adding S8PC #4 contest support and the new task; no unrelated modifications detected outside the stated objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch #3264

📝 Coding Plan

• Generate coding plan for human review comments

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[KATO-Hiro]

LGTM