Remove remaining legacy SourceInfo field dependencies

[rmanibus]

Context

core.SourceInfo is being simplified to use only the current identity model:

• Identity
• PathID
• DriveName

The legacy VolumeUUID and VolumeLabel fields were removed from the type, but several engine/CLI paths and tests still referenced them.

Goal

Finish the cleanup so runtime code, formatting, grouping, and tests all use the current SourceInfo fields consistently.

Scope

• remove remaining runtime references to deleted legacy fields
• update snapshot matching/grouping logic to rely on Identity/PathID
• update CLI table formatting to use DriveName
• update affected tests to use the new source identity model

Acceptance Criteria

• go test ./... passes
• golangci-lint run ./... passes
• no runtime code references SourceInfo.VolumeUUID or SourceInfo.VolumeLabel
• issue is tracked under milestone 1.14.0