fix(web): unify detail sidebar home control

[Jingyi-Dify]

Summary

Unifies the detail-sidebar home control so the arrow and home icon behave as a single navigation target.

• Replaces separate back buttons plus home links with a single home link in dataset, deployment, and agent detail sidebars.
• Keeps existing app detail sidebar behavior aligned with the same single-link contract.
• Adds focused regression coverage to assert the combined home control routes to / and does not expose a separate back button.

From Codex

Screenshots

Before	After
N/A	N/A

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods

Verification:

• CI=true pnpm -C web test app/components/app-sidebar/__tests__/dataset-detail-top.spec.tsx features/agent-v2/agent-detail/__tests__/navigation.spec.tsx features/deployments/detail/__tests__/index.spec.tsx
• CI=true pnpm -C web lint:tss
• git diff --check HEAD^ HEAD

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.33%. Comparing base (fc01d11) to head (b342b79).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #38487      +/-   ##
==========================================
- Coverage   85.35%   85.33%   -0.02%     
==========================================
  Files        5003     5004       +1     
  Lines      265290   265364      +74     
  Branches    50424    50457      +33     
==========================================
+ Hits       226426   226444      +18     
- Misses      34414    34470      +56     
  Partials     4450     4450              

Flag	Coverage Δ
dify-ui	94.72% <ø> (ø)
web	84.86% <ø> (-0.05%)	⬇️

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