grpcio-tools 1.82.0+ (including its 1.82.0 pre-releases) bundles a
protoc that emits protobuf 7.35.x gencode, which no protobuf 6 runtime
can load. Pin grpcio-tools below that (excluding pre-releases via the
'.dev0' trick, since a plain '<1.82' bound already let a 1.82.0rc
release slip through once) and add a CI check that verifies the
generated *_pb2.py files stay within the protobuf floor declared in
pyproject.toml.
Only the load-bearing bounds are kept: protobuf's '>=6.33.5' floor
(must match the emitted gencode) and grpcio-tools' '<1.82.0.dev0'
ceiling. Non-load-bearing bounds (protobuf's '<8', grpcio-tools'
'>=1.81') were dropped since they don't change dependency resolution
or protect against anything the above doesn't already cover.
