docs: add per-user NFS subpath example for OpenClaw

[Jayant-kernel]

Ⅰ. Describe what this PR does

This PR adds an English and Chinese OpenClaw guide for mounting an isolated NFS subpath for each SandboxClaim.

The guide:

• shows a complete dynamicVolumesMount claim for a per-user workspace;
• explains the CSI-backed PV, driver registration, and runtime injection prerequisites;
• documents how subPath is resolved against spec.csi.volumeAttributes.path;
• includes commands to wait for the claim and find the claimed Sandbox; and
• calls out path validation and the security boundary of subpath-based isolation.

Ⅱ. Does this pull request fix one issue?

Fixes #507

Ⅲ. Describe how to verify it

1. Follow the new OpenClaw NFS subpath section with a CSI-backed NFS PV and a SandboxSet configured for agent-runtime and CSI injection.
2. Apply the example SandboxClaim.
3. Verify that the claim reaches Completed and that the claimed Sandbox mounts the requested user subdirectory at /home/node/.openclaw/workspace.

Documentation formatting was checked with:

git diff --check

Ⅳ. Special notes for reviews

The dynamic mount path requires a CSI-backed PV. A legacy spec.nfs PV cannot be used because the implementation builds a CSI NodePublishVolumeRequest and resolves subPath through the PV's volumeAttributes.path.

[kruise-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign furykerry for approval by writing /assign @furykerry in a comment. For more information see:The Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.66%. Comparing base (ed4bff7) to head (da63949).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #559   +/-   ##
=======================================
  Coverage   79.66%   79.66%           
=======================================
  Files         194      194           
  Lines       13774    13774           
=======================================
  Hits        10973    10973           
  Misses       2403     2403           
  Partials      398      398           

Flag	Coverage Δ
unittests	79.66% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.