rename_file wrote server-provided reference edits before creating the
destination parent and moving the source, with no rollback. A failed
mkdir/rename (e.g. EXDEV across mounts, EACCES) left the reference files
rewritten while the source stayed put, violating the atomic "moves file
AND rewrites all imports/references" contract.
Extract applyEditsThenRename in lsp/edits.ts: snapshot each edited file,
apply edits, then mkdir+rename; on failure restore every snapshot before
rethrowing. Rewire the rename_file handler to build the summary and hand
the edits to the helper.
Fixes#8379
