feat: add package/build.sh cross-platform build script

- build.sh supports linux/amd64, linux/arm64, darwin/amd64, darwin/arm64,
  windows/amd64, and 'all' for matrix build
- Components: homed (CGO, Linux/macOS-only), waiter (all platforms), gui
- Platform matrix documented in script header
- waiter: extract setRawMode into rawmode_linux.go + rawmode_other.go for
  cross-platform support
- Add cmd/gui/node_modules/ and dist/ to .gitignore
- Fix .gitignore waiter pattern to not ignore cmd/waiter/ directory

cmd/waiter/rawmode_defs.go

@@ -0,0 +1,18 @@
+package main
+
+type termios struct {
+	Iflag  uint32
+	Oflag  uint32
+	Cflag  uint32
+	Lflag  uint32
+	Cc     [20]byte
+	Ispeed uint32
+	Ospeed uint32
+}
+
+const (
+	TCGETS = 0x5401
+	TCSETS = 0x5402
+	ICANON = 0x2
+	ECHO   = 0x8
+)