[Issacboy123]

Summary

Prevents saved child sessions from being left behind when their parent session is deleted. Diffex now moves the selected parent's child-session directory to trash before deleting the parent. It keeps the parent when child cleanup is unsafe or fails, and clearly reports when the child data was removed but the parent could not be deleted.

Reasoning

Deleting owned child data before the parent prevents an otherwise unreachable namespace from being orphaned. Deriving the target from the validated parent header, proving containment, and rejecting link-like components prevents deletion from escaping the selected parent's ownership boundary. Reusing the session selector's trash behavior keeps cleanup recoverable; failing closed before parent deletion preserves the user's entry point when child cleanup cannot be verified.

Changes

• Added a validated helper that derives and checks the exact parent-owned child-session directory from the parent session header.
• Moved an existing owned directory to trash before deleting the parent and treated an absent namespace or owned directory as success.
• Rejected unsafe namespace and owned-directory files or links and verified that a reported trash operation actually removed the directory.
• Retained the parent when owned cleanup failed and reported partial deletion when parent removal failed or threw after cleanup.
• Preserved sibling child namespaces and kept child files excluded from normal session listing.
• Added focused deletion, containment, ordering, absence, cleanup-failure, partial-failure, and listing regressions.

Testing

• node ../../node_modules/vitest/dist/cli.js --run test/suite/subagent-persistence.test.ts test/suite/subagent-services.test.ts test/suite/subagent-registration.test.ts test/suite/agent-session-harness-version.test.ts test/session-manager/fork-branch.test.ts test/session-selector-path-delete.test.ts
• npm run check

[Pepps233]

This is needed, thank you