Scala/Rust brace-selector imports split before the prefix is distributed (a.b.{C, D} → a.b. C, D): Scala import recall 33% #3595

Problem

galaxyscope.extract_raw_imports handles a brace-selector import by deleting the braces and then splitting on commas. So

import io.circe.{ Decoder, Json }

records the tokens io.circe. Decoder (with a space) and a bare Json. Neither resolves: the first carries a space, and the second has lost its package. Rust's use a::{b, c} goes through the same code.

Measured

tests/tools/import_graph_accuracy.py scala (circe/circe, added in #3594): precision 99.4%, recall 33.0%, 674 missed imports. Examples from TodoService.scala and AtBenchmark.scala:

• io.circe.{ DecodingFailure, Errors } → Errors and io.circe. DecodingFailure
• io.circe.{ Decoder, Json } → Json and io.circe. Decoder

Fix direction

In extract_raw_imports, expand prefix{a, b => c, _} into prefix + each selector before the comma split:

• the prefix is everything before {, keeping its trailing . or ::;
• b => c keeps b;
• _ and * are wildcards.

This helps both Scala and Rust. Some of the remaining Scala misses are wildcard imports of package objects (io.circe.syntax._ → syntax/package.scala), which need a resolver rule; check them with --samples after the split fix.