fix: skip decommission status for unsupported topology

[ccccpj]

Description

Fix the Pool Decommission page so it determines topology support from the pools overview before requesting decommission status.

The page previously started /pools/list, /rebalance/status, and /decommission/status together. In a single-pool deployment, the backend intentionally does not provide decommission status and returns 501, so the otherwise valid unsupported topology was rendered as Load Failed.

This change:

• loads the pools overview first;
• skips /decommission/status when supportState is unsupported;
• renders the trusted single-pool state as Unsupported with no mutation actions;
• preserves fail-closed behavior for overview failures and supported-topology status failures;
• keeps rebalance and decommission status reads concurrent after a supported overview.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Performance improvement
• Test improvements
• Security fix

Testing

• Unit tests added/updated
• Manual testing completed

pnpm install --frozen-lockfile
pnpm type-check
pnpm lint
pnpm test:run
pnpm prettier --check 'app/(dashboard)/pool-decommission/page.tsx' lib/pool-decommission-load.ts tests/lib/pool-decommission-load.test.ts tests/lib/pool-operations-safety.test.js
git diff --check

• pnpm test:run: 392 tests passed.
• Deterministic regression coverage verifies unsupported single-pool status calls are 0, supported multi-pool status calls occur, overview failures stop dependent reads, and supported status failures reject.
• Adversarial reviewer, tester, UX, and simplifier passes completed.
• Full pnpm format:check remains blocked by the unchanged upstream file components/object/tiff-viewer.tsx; every file in this PR passes Prettier.

Checklist

• Code follows the project's style guidelines
• Self-review completed
• TypeScript types are properly defined
• All commit messages are in English (Conventional Commits)
• All existing tests pass
• No new dependencies added, or they are justified

Related Issues

Fixes rustfs/rustfs#5773

Screenshots (if applicable)

The after captures use a deterministic local mock with one active 1 TiB pool. The mock returns 501 for /decommission/status, matching the reported backend behavior.

Before

After

Desktop

Mobile

Additional Notes

This PR does not change the RustFS backend's 501 contract for unsupported single-pool decommission status. Supported multi-pool status failures continue to render an error and keep interactions locked.