Question: Confirming v1.4.1 decoder compatibility with v1.5.7 encoder output

This is a compatibility confirmation question, not a bug — I'm using this template because it's
the only one available. No decoding failure has been observed.

Prior art in this repository:

- #3110 "ZSTD compatibility" — @Cyan4973 confirmed with "Yes" that v1.5.2 output can be decoded
by v1.4.5; @terrelln stated "Zstd will always be compatible with older versions."
- #3711 "Compatibility between compress/decompress APIs" — asked in the RocksDB context;
@Cyan4973 confirmed "Already deployed decoders will have no problem decoding new frames with
checksum enabled."

Given the above official guarantees, I would like a targeted confirmation for our specific
downgrade scenario before executing it on a multi-TB production deployment.

Scenario

We are planning to upgrade zstd from v1.4.1 to v1.5.7 in a distributed RocksDB-based KV storage
cluster (zstd is statically linked into each node's binary). The upgrade will be done as a
rolling deployment across dozens of nodes; during the rolling window, the cluster is in a
mixed-version state:

1. Upgrade mid-state (unavoidable, lasts hours to days per cluster): nodes still on v1.4.1 must
be able to decode SSTs / raft snapshots produced by peers running v1.5.7. A single Raft
replication group typically contains 3 replicas that may straddle the version boundary.
2. Rollback scenario (safety-net requirement): if we need to roll a node back from v1.5.7 to
v1.4.1, that node's decoder must still handle data that was written while it was on v1.5.7.

Both cases boil down to the same technical question: "Can a v1.4.1 decoder correctly decompress
every frame produced by a v1.5.7 encoder under our configuration?"

Question

Given the above encoder-side constraints, can a v1.4.1 decoder be guaranteed to correctly
decompress every frame produced by the v1.5.7 encoder, including dictionary-compressed blocks?

Reading #3110 and #3711, our understanding is "yes." We would appreciate a one-line confirmation
for the record, so we can attach it to our internal rollback decision document.