test(core): extract test harness cleanup

[IzumiSy]

Motivation

PR #525 combines an oxlint upgrade, production state-ownership changes, a DataTable API addition, and test cleanup. Reviewing those concerns together makes it difficult to distinguish mechanical changes from behavior changes.

This PR extracts only the independently mergeable test cleanup onto the latest main, as the first step toward landing the larger change incrementally. It does not require the compiler-oriented production refactors or the newer lint version.

Design Decision

Keep the existing implementation and contracts as the baseline

Production code, public APIs, dependencies, lint settings, snapshots, and generated documentation remain unchanged. New regression tests associated with the deferred behavior/API changes are not included. Existing test cases are retained.

Preserve integration boundaries

Use renderHook for hook-only assertions instead of render-time/global result capture. Keep the routed layout around scroll-container tests, and retain integrated harnesses for DataTable DOM tests and React Hook Form so hook/UI lifecycle behavior is not changed by the cleanup. Navigation setup stays outside React render.

The changes are organized into two commits: fixture/Suspense cleanup, followed by hook-result cleanup.

Summary

• Move reusable test components, mock factories, and stateless helpers out of nested test scopes.
• Read theme, breadcrumb, scroll-container, and DataTable hook results directly through renderHook, without detached DOM harnesses or manual UI synchronization.
• Assert auth suspension through the actual Suspense fallback rather than render-time bookkeeping, and label the Tooltip test fixture.

[github-actions]

Code Metrics Report

	main (d8d4ec3)	#600 (3ce3e11)	+/-
Coverage	88.6%	88.6%	0.0%
Test Execution Time	1m53s	1m46s	-7s

Details

  |                     | main (d8d4ec3) | #600 (3ce3e11) | +/-  |
  |---------------------|----------------|----------------|------|
  | Coverage            |          88.6% |          88.6% | 0.0% |
  |   Files             |            208 |            208 |    0 |
  |   Lines             |           6263 |           6263 |    0 |
  |   Covered           |           5552 |           5552 |    0 |
+ | Test Execution Time |          1m53s |          1m46s |  -7s |

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Reported by octocov