test(08-07): add failing repeatable-flag RED anchor for bonfire

- TestPhase8RedBonfireFlags asserts Input.Flags preserves ordered
  repeated --redirect-uri/--scope values while existing scalar --mode
  flags via Input.Flag stay unaffected
- Adds the compiling seam (Flag.Repeatable, Input.Flags,
  cobraInput.Flags) without wiring Cobra StringSlice registration yet,
  so the test fails with PHASE8_RED:bonfire-flags (D-19)

bonfire/command.go

@@ -28,6 +28,13 @@ type Flag struct {
 	Default     string
 	// Bare allows --flag without a value; cobra stores "true".
 	Bare bool
+	// Repeatable registers this flag as an ordered, multi-occurrence
+	// string flag (Cobra StringSlice) instead of a scalar string flag
+	// (08-CONTEXT.md D-19; 08-PATTERNS.md "bonfire repeatable-flag gap").
+	// Repeated `--name=a --name=b` preserves insertion order and is read
+	// back through Input.Flags, never Input.Flag. Existing scalar/bare
+	// flags are unaffected: Repeatable defaults to false.
+	Repeatable bool
 }
 
 // Arg describes a positional argument.
@@ -42,6 +49,10 @@ type Input interface {
 	Args() []string
 	Argument(name string) (string, bool)
 	Flag(name string) (string, bool)
+	// Flags returns the ordered, repeated values of a Repeatable flag
+	// (D-19). It returns nil for a scalar/bare flag or an unset repeatable
+	// flag; callers must use Flag for scalar flags.
+	Flags(name string) []string
 }
 
 type cobraInput struct {
@@ -64,6 +75,20 @@ func (in cobraInput) Argument(name string) (string, bool) {
 	return "", false
 }
 
+// Flags returns the ordered values of a Repeatable (Cobra StringSlice)
+// flag. It returns nil if the flag was never registered as repeatable
+// (wrong pflag type) or the command has no flag set (08-CONTEXT.md D-19).
+func (in cobraInput) Flags(name string) []string {
+	if in.cmd == nil || in.cmd.Flags() == nil {
+		return nil
+	}
+	vals, err := in.cmd.Flags().GetStringSlice(name)
+	if err != nil {
+		return nil
+	}
+	return vals
+}
+
 func (in cobraInput) Flag(name string) (string, bool) {
 	if in.cmd == nil || in.cmd.Flags() == nil {
 		return "", false