Add option to select output file role

- Serving files from target dir, filesystem during dev: output with source role (don't include in classpath)
- Uberjar production build: resource role, include in JAR
- Cljs-test: don't add files to fileset, test runner can use files from tmp-dir without messing up the fileset

The issue names no files or tests. Start by locating the task entry points that handle target-directory serving, uberjar resource inclusion, and cljs-test filesets; then trace how output roles are represented. Done means each stated environment applies the intended role without altering the others, with coverage for those three cases.

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