chore(deps): grpc 4→5, protobuf 4→6

Two coupled majors that have been blocking the rest of the
Dart-side dependency lift in Studio (the constraint solver
pins meta/characters/etc. through these). Picked up:

- grpc 5.1.0 (was 4.2.0)
- protobuf 6.0.0 (was 4.2.0)
- analyzer 13.0.0, _fe_analyzer_shared 100.0.0
- google_cloud 0.5.0, googleapis_auth 2.3.1 (transitive)

The bindings now live in `lib/src/generated/fai/v1/` only —
the well-known-types `lib/src/generated/google/protobuf/`
copy has been deleted. protobuf 6 ships its own bundled
`well_known_types/google/protobuf/empty.pb.dart` and the
`HubAdminClient` API expects the *packaged* Empty type;
emitting a local copy created two distinct Empty types and
broke every `_admin.<rpc>(Empty())` call site.

`tools/generate.sh` now skips the WKT generation pass and
wipes `lib/src/generated/google/` on every run so the
duplicate-types breakage can't regress silently. The
import in `hub_client.dart` switches from the local copy to
`package:protobuf/well_known_types/google/protobuf/empty.pb
.dart`.

Smoke-verified: dart analyze clean, dart test green
(4 tests). Bumped to 0.17.0 — Studio absorbs in the next
commit.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

tools/generate.sh

@@ -55,9 +55,13 @@ if [[ ${#PROTO_FILES[@]} -eq 0 ]]; then
   exit 1
 fi
 
-# Locate the well-known-types include directory. Required so we
-# can generate Dart bindings for google.protobuf.Empty,
-# google.protobuf.Struct, etc. that the platform's protos import.
+# Locate the well-known-types include directory. Only needed
+# for protoc's resolver; we do NOT generate the WKT Dart files
+# anymore — `package:protobuf` (6.x+) ships them as
+# `well_known_types/google/protobuf/empty.pb.dart` etc., and
+# emitting our own copy creates duplicate-Empty-type errors at
+# the API boundary (HubAdminClient expects the packaged Empty,
+# our local copy is a distinct type to the analyser).
 WKT_INCLUDE=""
 for candidate in \
   "/opt/homebrew/include" \
@@ -75,23 +79,22 @@ if [[ -z "$WKT_INCLUDE" ]]; then
   exit 1
 fi
 
-WKT_PROTOS=(
-  "$WKT_INCLUDE/google/protobuf/empty.proto"
-  "$WKT_INCLUDE/google/protobuf/struct.proto"
-  "$WKT_INCLUDE/google/protobuf/timestamp.proto"
-)
+# Wipe any stale WKT files generated by an earlier (pre-
+# protobuf-6) version of this script. Keeping them around
+# silently revives the duplicate-types breakage above on
+# regen.
+rm -rf "$OUT_DIR/google"
 
 echo "generating Dart bindings"
 echo "  protos: ${#PROTO_FILES[@]} files under $PROTO_ROOT"
-echo "  WKT include: $WKT_INCLUDE"
+echo "  WKT include: $WKT_INCLUDE (protoc resolver only)"
 echo "  output: $OUT_DIR"
 
 protoc \
   --proto_path="$PROTO_ROOT" \
   --proto_path="$WKT_INCLUDE" \
   --dart_out=grpc:"$OUT_DIR" \
-  "${PROTO_FILES[@]}" \
-  "${WKT_PROTOS[@]}"
+  "${PROTO_FILES[@]}"
 
 echo "done. generated files:"
 find "$OUT_DIR" -name '*.dart' | sort