feat(01-01): boot hello app and dispatch greeter:hello

- Add party plugin registry with Register-before-Boot activation
- Add backpack, compass, bonfire, and pact capability interfaces
- Add examples/hello with two compiled plugin modules

bonfire/command.go

@@ -0,0 +1,110 @@
+package bonfire
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"github.com/spf13/cobra"
+)
+
+// Command is a console command value collected from plugins or the tool.
+type Command struct {
+	Name        string
+	Description string
+	Flags       []Flag
+	Args        []Arg
+	Run         func(ctx context.Context, in Input, out Output) error
+}
+
+// Flag describes a string flag passed to a command.
+type Flag struct {
+	Name        string
+	Shorthand   string
+	Description string
+	Default     string
+}
+
+// Arg describes a positional argument.
+type Arg struct {
+	Name        string
+	Description string
+	Required    bool
+}
+
+// Input is the parsed argument and flag view handed to Command.Run.
+type Input interface {
+	Args() []string
+	Argument(name string) (string, bool)
+	Flag(name string) (string, bool)
+}
+
+// Output is an injected writer used by commands instead of package-level stdout.
+type Output interface {
+	io.Writer
+	Println(a ...any)
+	Printf(format string, a ...any)
+}
+
+type cobraInput struct {
+	cmd  *cobra.Command
+	spec Command
+	args []string
+}
+
+func (in cobraInput) Args() []string { return in.args }
+
+func (in cobraInput) Argument(name string) (string, bool) {
+	for i, arg := range in.spec.Args {
+		if arg.Name == name {
+			if i < len(in.args) {
+				return in.args[i], true
+			}
+			return "", false
+		}
+	}
+	return "", false
+}
+
+func (in cobraInput) Flag(name string) (string, bool) {
+	if in.cmd == nil || in.cmd.Flags() == nil {
+		return "", false
+	}
+	if !in.cmd.Flags().Changed(name) {
+		val, err := in.cmd.Flags().GetString(name)
+		if err != nil || val == "" {
+			return "", false
+		}
+		return val, true
+	}
+	val, err := in.cmd.Flags().GetString(name)
+	if err != nil {
+		return "", false
+	}
+	return val, true
+}
+
+type writerOutput struct {
+	w io.Writer
+}
+
+func (o writerOutput) Write(p []byte) (int, error) {
+	if o.w == nil {
+		return 0, io.ErrClosedPipe
+	}
+	return o.w.Write(p)
+}
+
+func (o writerOutput) Println(a ...any) {
+	if o.w == nil {
+		return
+	}
+	fmt.Fprintln(o.w, a...)
+}
+
+func (o writerOutput) Printf(format string, a ...any) {
+	if o.w == nil {
+		return
+	}
+	fmt.Fprintf(o.w, format, a...)
+}