fix: background workers not spawning in compiled binary

[aman7625]

What

• When installed via the install script (compiled binary), ws run reports success but agents never start - they remain stuck in queued status forever
• Added a buildBgArgs() helper that detects compiled vs source mode and spawns [process.execPath, ...] for compiled binaries, ["bun", Bun.main, ...] for source

Why

• The background workers are spawned using ["bun", Bun.main, "run", ...]. In a compiled binary, Bun.main points to the binary itself, so it tries to run bun /usr/local/bin/ws run ... - which silently fails since you can't pass a compiled Bun binary through bun

Test plan

• bun test passes
• Tested manually with ws CLI
• Tested by building both a broken and fixed binary locally with bun build --compile --target bun-darwin-arm64 and comparing both behaviours.