chore(docs): Add details for network clean-up between tenants

[bcavnvidia]

Related issues

#2152

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No testing required (docs, internal refactor, etc.)

Additional Notes

Closes #2152

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📥 Commits

Reviewing files that changed from the base of the PR and between 2a09d0e and 727b978.

📒 Files selected for processing (2)

• docs/operations/tenant-lifecycle-cleanup.md
• docs/overview/lifecycle.md

✅ Files skipped from review due to trivial changes (1)

• docs/operations/tenant-lifecycle-cleanup.md

🚧 Files skipped from review as they are similar to previous changes (1)

• docs/overview/lifecycle.md

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Summary by CodeRabbit

• Documentation
  • Expanded tenant lifecycle guidance with more detail on how hosts are cleaned up between tenants, including tenant network removal and fail-closed tenant-free defaults.
  • Added verification steps, troubleshooting guidance for hosts stuck in cleanup-related states, and concrete operator commands for cleanup status checks.
  • Clarified the conditions for when a host is fully released and safe to return to the available pool, based on post-tenant network transition confirmation.

Walkthrough

This PR expands tenant-sanitization documentation with explicit network cleanup behavior between tenants. It adds an operations guide for teardown, verification, and troubleshooting, and updates the lifecycle overview with a more detailed release sequence.

Changes

Tenant Network Cleanup Documentation

Layer / File(s)	Summary
Network cleanup operational reference docs/operations/tenant-lifecycle-cleanup.md	Adds a "Network Cleanup (Between Tenants)" section with a concern-to-action table, verification CLI commands, and troubleshooting guidance for stuck cleanup states.
Lifecycle overview sanitization narrative update docs/overview/lifecycle.md	Replaces the concise cleanup list with prose detailing network teardown, fail-closed tenant-free state, route/IP/VNI/DPU allocation cleanup, DHCP/metadata reconfiguration, and release gating on DPU confirmation.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the documentation update for tenant network cleanup.
Description check	✅ Passed	The description is on-topic and matches the documented network cleanup changes.
Linked Issues check	✅ Passed	The docs additions cover the requested cleanup steps: detaching tenant networking, restoring admin state, DHCP changes, and route/BGP withdrawal.
Out of Scope Changes check	✅ Passed	The PR appears limited to relevant documentation updates with no unrelated code or scope additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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