feat(cli): add Go 1.26 iterators and modernise idioms

- Add Children() iter.Seq on TreeNode for range-based traversal
- Add RegisteredCommands() iter.Seq on command registry (mutex-safe)
- Add Regions()/Slots() iterators on Composite layout
- Add Tasks()/Snapshots() iterators on TaskTracker (mutex-safe)
- Use strings.FieldsSeq, strings.SplitSeq in parseMultiSelection
- Use range-over-int where applicable

Co-Authored-By: Gemini <noreply@google.com>
Co-Authored-By: Virgil <virgil@lethean.io>

.gitignore

@@ -23,3 +23,4 @@ local.test
 
 patch_cov.*
 go.work.sum
+.kb

pkg/cli/commands.go

@@ -3,6 +3,7 @@ package cli
 
 import (
 	"context"
+	"iter"
 	"sync"
 
 	"forge.lthn.ai/core/go/pkg/framework"
@@ -65,6 +66,19 @@ func RegisterCommands(fn CommandRegistration) {
 	}
 }
 
+// RegisteredCommands returns an iterator over the registered command functions.
+func RegisteredCommands() iter.Seq[CommandRegistration] {
+	return func(yield func(CommandRegistration) bool) {
+		registeredCommandsMu.Lock()
+		defer registeredCommandsMu.Unlock()
+		for _, fn := range registeredCommands {
+			if !yield(fn) {
+				return
+			}
+		}
+	}
+}
+
 // attachRegisteredCommands calls all registered command functions.
 // Called by Init() after creating the root command.
 func attachRegisteredCommands(root *cobra.Command) {
@@ -76,3 +90,4 @@ func attachRegisteredCommands(root *cobra.Command) {
 	}
 	commandsAttached = true
 }
+

pkg/cli/layout.go

@@ -1,6 +1,9 @@
 package cli
 
-import "fmt"
+import (
+	"fmt"
+	"iter"
+)
 
 // Region represents one of the 5 HLCRF regions.
 type Region rune
@@ -26,6 +29,28 @@ type Composite struct {
 	parent  *Composite
 }
 
+// Regions returns an iterator over the regions in the composite.
+func (c *Composite) Regions() iter.Seq[Region] {
+	return func(yield func(Region) bool) {
+		for r := range c.regions {
+			if !yield(r) {
+				return
+			}
+		}
+	}
+}
+
+// Slots returns an iterator over the slots in the composite.
+func (c *Composite) Slots() iter.Seq2[Region, *Slot] {
+	return func(yield func(Region, *Slot) bool) {
+		for r, s := range c.regions {
+			if !yield(r, s) {
+				return
+			}
+		}
+	}
+}
+
 // Slot holds content for a region.
 type Slot struct {
 	region Region

pkg/cli/tracker.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"fmt"
 	"io"
+	"iter"
 	"os"
 	"strings"
 	"sync"
@@ -83,6 +84,33 @@ type TaskTracker struct {
 	started bool
 }
 
+// Tasks returns an iterator over the tasks in the tracker.
+func (tr *TaskTracker) Tasks() iter.Seq[*TrackedTask] {
+	return func(yield func(*TrackedTask) bool) {
+		tr.mu.Lock()
+		defer tr.mu.Unlock()
+		for _, t := range tr.tasks {
+			if !yield(t) {
+				return
+			}
+		}
+	}
+}
+
+// Snapshots returns an iterator over snapshots of tasks in the tracker.
+func (tr *TaskTracker) Snapshots() iter.Seq2[string, string] {
+	return func(yield func(string, string) bool) {
+		tr.mu.Lock()
+		defer tr.mu.Unlock()
+		for _, t := range tr.tasks {
+			name, status, _ := t.snapshot()
+			if !yield(name, status) {
+				return
+			}
+		}
+	}
+}
+
 // NewTaskTracker creates a new parallel task tracker.
 func NewTaskTracker() *TaskTracker {
 	return &TaskTracker{out: os.Stdout}

pkg/cli/tree.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"fmt"
+	"iter"
 	"strings"
 )
 
@@ -55,6 +56,17 @@ func (n *TreeNode) WithStyle(style *AnsiStyle) *TreeNode {
 	return n
 }
 
+// Children returns an iterator over the node's children.
+func (n *TreeNode) Children() iter.Seq[*TreeNode] {
+	return func(yield func(*TreeNode) bool) {
+		for _, child := range n.children {
+			if !yield(child) {
+				return
+			}
+		}
+	}
+}
+
 // String renders the tree with box-drawing characters.
 // Implements fmt.Stringer.
 func (n *TreeNode) String() string {

pkg/cli/utils.go

@@ -427,12 +427,14 @@ func ChooseMulti[T any](prompt string, items []T, opts ...ChooseOption[T]) []T {
 // Returns 0-based indices.
 func parseMultiSelection(input string, maxItems int) ([]int, error) {
 	selected := make(map[int]bool)
-	parts := strings.Fields(input)
 
-	for _, part := range parts {
+	for part := range strings.FieldsSeq(input) {
 		// Check for range (e.g., "1-3")
 		if strings.Contains(part, "-") {
-			rangeParts := strings.Split(part, "-")
+			var rangeParts []string
+			for p := range strings.SplitSeq(part, "-") {
+				rangeParts = append(rangeParts, p)
+			}
 			if len(rangeParts) != 2 {
 				return nil, fmt.Errorf("invalid range: %s", part)
 			}
@@ -464,7 +466,7 @@ func parseMultiSelection(input string, maxItems int) ([]int, error) {
 
 	// Convert map to sorted slice
 	result := make([]int, 0, len(selected))
-	for i := 0; i < maxItems; i++ {
+	for i := range maxItems {
 		if selected[i] {
 			result = append(result, i)
 		}
@@ -472,6 +474,7 @@ func parseMultiSelection(input string, maxItems int) ([]int, error) {
 	return result, nil
 }
 
+
 // ChooseMultiAction prompts for multiple selections using grammar composition.
 //
 //	files := ChooseMultiAction("select", "files", files)