Doctor flags a shipped binary that's still carrying the build-time
placeholder so `uatu test` won't silently fail trying to launch a
nonexistent sidecar. Makefile uatu target now copies the freshly
built fat JAR into the embed directory before `go build`.
Each check is a value so tests can swap in fakes. Java check parses
both legacy (1.8) and modern (17+) version strings. Emulator check
falls back to ANDROID_HOME/emulator/emulator since the brew cask
ships it without putting it on PATH.