Fix stale Rift parent and workspace name resolution

[dbpolito]

Ticket

SKIPPED

Description

Prevent stale OpenCode workspace metadata from nesting new Rift workspaces beneath a removed managed parent. Normalize cached Rift paths back to the original checkout and select an available suffixed name before OpenCode registers a workspace, keeping OpenCode and Rift aligned without global registry cleanup.

Checklist

Parent Resolution

• Normalize cached managed-workspace paths to the original Rift source
• Register new workspaces beneath the project-level Rift directory

Name Resolution

• Detect names already present in the Rift registry
• Select a concise numeric suffix before workspace registration
• Preserve transactional mismatch rollback

Validation

• Verify that bun run compile succeeds
• Confirm that bun run typecheck reports no errors
• Check that all 82 tests pass with bun run test