feat(memory): bind the memory engine as a loadable TinyBus module - #5512

Reviewed 7 files; 3 findings. The code index for this repository is cold, so this review saw the diff alone.

No findings.

Fixed since the last review

• Round-trip test claims to fill every field but uses Default for the rest
• Cover ExportRecord, ImportOutcome and SourceScope serde crossings
• Pin the Module pass-through policy in redact_outbound
• Round-trip test claims to fill every field but uses Default for the rest — fixed: the OwnedRecallOpts literal sets every field explicitly with no ..Default::default(), and the comment documents the deliberate omission.
• Cover ExportRecord, ImportOutcome and SourceScope serde crossings — fixed: three dedicated tests now round-trip each type.
• Pin the Module pass-through policy in redact_outbound — not applicable to this file; redact_outbound does not appear in module_adapter_tests.rs.
• Pin the Module pass-through policy in redact_outbound
• Round-trip test claims to fill every field but uses Default for the rest — not present in boot.rs; cannot verify here.
• Cover ExportRecord, ImportOutcome and SourceScope serde crossings — not present in boot.rs; cannot verify here.
• Pin the Module pass-through policy in redact_outbound — not present in boot.rs; cannot verify here.