Mill doesn't check local Ivy repository

Question

Mill doesn't seem to check the local Ivy cache for (snapshot) dependencies. I've got a local build of a dependency I want to use - Mill can't find it. The output shows it searching my registered Maven repos:

  def repositoriesTask = T.task {
    super.repositoriesTask() ++ Seq(
            MavenRepository("https://oss.sonatype.org/content/repositories/snapshots"),
      ...

but not the local ivy2 cache. I would have thought that would just work by default.

I tried adding it explicitly as a repo:

      MavenRepository("file://~/.ivy2/local/"),

but that results in a Java error ("URI has an authority component").

I feel like I must be missing something basic. I don't see this covered in the Mill docs.

EDIT - MORE INFO:

build.sc dependency (part of ivyDeps):

    ivy"com.devsisters::shardcake-entities:2.0.6+1-f0528bd1+20230425-1217-SNAPSHOT",

Directory listing:

me in ~/dev/project on branch main > ls ~/.ivy2/local/com.devsisters/shardcake-entities_2.13 
2.0.6+1-f0528bd1+20230425-1217-SNAPSHOT
me in ~/dev/project on branch main > ls ~/.ivy2/local/com.devsisters/shardcake-entities_2.13/2.0.6+1-f0528bd1+20230425-1217-SNAPSHOT
docs    ivys    jars    poms    srcs