fix(core): expose previous accepted move path

[phernandez]

Why

Accepted note moves capture the authoritative previous file path inside the move transaction, but exposed it only when materialized-file cleanup was needed. Never-materialized moves therefore forced Cloud activity publishing into a racy pre-read.

What changed

• carry previous_file_path on accepted materialization results independently from cleanup work
• set it from the transaction-local source path for moves only
• preserve the field through queue-neutral requests and serialized worker payloads
• keep create and update results unchanged
• cover materialized and never-materialized moves plus create/update absence

Verification

• just fast-check
• just fast-test — 135 passed, 1 skipped
• focused runtime, payload, mutation, enqueue, and response tests — 46 passed

Closes #1072.

Cloud follow-up: basicmachines-co/basic-memory-cloud#1506.