refactor(launcher): complete split into modular launcher/ directory

- Split 4,028-line monolithic subminer script into 10 focused modules
- launcher/types.ts: shared types and constants
- launcher/log.ts: logging infrastructure
- launcher/util.ts: pure utilities and child process runner
- launcher/config.ts: config loading and arg parsing
- launcher/jimaku.ts: Jimaku API client and media parsing
- launcher/picker.ts: rofi/fzf menu UI
- launcher/mpv.ts: mpv process management and IPC
- launcher/youtube.ts: YouTube subtitle generation pipeline
- launcher/jellyfin.ts: Jellyfin API and browsing
- launcher/main.ts: orchestration entrypoint
- Add build-launcher Makefile target using bun build
- subminer is now a build artifact produced by make build-launcher
- install-linux and install-macos depend on build-launcher

.gitignore

@@ -6,6 +6,9 @@ out/
 dist/
 release/
 
+# Launcher build artifact (produced by make build-launcher)
+subminer
+
 # Logs
 *.log
 npm-debug.log*