Enhanced Pod Snapshot Management (Persistence, List, Delete)

[shrutiyam-glitch]

Depends on: #249

This PR extends the PodSnapshotSandboxClient to support the full lifecycle of pod snapshots, introducing local metadata persistence, listing capabilities, and deletion logic.

Key Changes:

• Snapshot Persistence (SnapshotPersistenceManager):
  -- Added local metadata storage (~/.snapshot_metadata/.snapshots.json) to track created snapshots.
  -- Metadata includes snapshot_uid, creationTimestamp, policy_labels, policy_name and claim_name.
  -- The snapshot() method now automatically saves snapshot metadata upon successful creation.
• list_snapshots():
  -- Lists valid snapshots from local metadata. Supports filtering by policy_name and ready_only status.
  -- Returns a list of dictionaries sorted by creation timestamp (newest first).
• delete_snapshots():
  -- Deletes both the PodSnapshot resources from the cluster.
  -- Cleans up the corresponding local metadata.
  -- Returns the total count of successfully deleted snapshots.
  -- Can delete a specific snapshot by snapshot_uid or ALL tracked snapshots if no name is provided.

Helper Methods:

• Added _get_policy_info to fetch labels from the PodSnapshot and PodSnapshotPolicy resources for metadata storage.

Testing:

• Unit Tests: Added
  agentic_sandbox/gke_extensions/test_podsnapshot_client.py

• Integration Test:
  -- Updated test_podsnapshot_extension.py to verify the new listing and deletion workflows.
  -- Lists existing ready snapshots after creation.
  -- Deletes all snapshots at the end of the test and verifies the deletion count.

Output:

python3 test_podsnapshot_extension.py --labels app=agent-sandbox-workload --template-name python-counter-template --namespace sandbox-test
--- Starting Sandbox Client Test (Namespace: sandbox-test, Port: 8888) ---

***** Phase 1: Starting Counter *****

======= Testing Pod Snapshot Extension =======
Creating first pod snapshot 'test-snapshot-10' after 10 seconds...
Trigger Name: test-snapshot-10-42155a16
Snapshot UID: f0a06afd-2b9a-4f03-bf0e-db18da33881f
Success: True
Error Code: 0
Error Reason: 

Creating second pod snapshot 'test-snapshot-20' after 10 seconds...
Trigger Name: test-snapshot-20-963ea265
Snapshot UID: 385eb33e-6d81-4515-9ce8-16bd810003a6
Success: True
Error Code: 0
Error Reason: 
Recent snapshot UID: 385eb33e-6d81-4515-9ce8-16bd810003a6

***** List all existing ready snapshots with the policy name. *****
Snapshot ID: 385eb33e-6d81-4515-9ce8-16bd810003a6, Source Pod: sandbox-claim-ce2c1e4a, Creation Time: 2026-02-19T22:57:12Z, Policy Name: example-psp-workload
Snapshot ID: f0a06afd-2b9a-4f03-bf0e-db18da33881f, Source Pod: sandbox-claim-ce2c1e4a, Creation Time: 2026-02-19T22:56:59Z, Policy Name: example-psp-workload

***** Phase 2: Restoring from most recent snapshot & Verifying *****

Waiting 5 seconds for restored pod to resume printing...
Pod was restored from the most recent snapshot.

**** Deleting snapshots *****
Deleted Snapshots: 2
--- Pod Snapshot Test Passed! ---

--- Sandbox Client Test Finished ---

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[k8s-ci-robot]

Hi @shrutiyam-glitch. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[k8s-ci-robot]

@shrutiyam-glitch: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
presubmit-agent-sandbox-unit-test	756a4c4	link	true	/test presubmit-agent-sandbox-unit-test
presubmit-test-autogen-up-to-date	756a4c4	link	true	/test presubmit-test-autogen-up-to-date
presubmit-agent-sandbox-e2e-test	756a4c4	link	true	/test presubmit-agent-sandbox-e2e-test

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[k8s-ci-robot]

PR needs rebase.

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