feat: workspace metadata model with YAML read/write

TaskMeta struct matching task.yaml schema exactly. Tests for roundtrip, field presence, and archive state.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/workspace/metadata.go

@@ -0,0 +1,45 @@
+package workspace
+
+import (
+	"os"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+// TaskMeta represents the task.yaml schema. Exactly these fields, no extras in v0.1.
+type TaskMeta struct {
+	ID            string     `yaml:"id"`
+	Slug          string     `yaml:"slug"`
+	Title         string     `yaml:"title"`
+	CreatedAt     time.Time  `yaml:"created_at"`
+	UpdatedAt     time.Time  `yaml:"updated_at"`
+	Status        string     `yaml:"status"`
+	Category      string     `yaml:"category"`
+	Mode          string     `yaml:"mode"`
+	Agent         string     `yaml:"agent"`
+	WorkspacePath string     `yaml:"workspace_path"`
+	ArchivedAt    *time.Time `yaml:"archived_at"`
+}
+
+// WriteMeta writes a TaskMeta to a YAML file.
+func WriteMeta(path string, meta *TaskMeta) error {
+	data, err := yaml.Marshal(meta)
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(path, data, 0644)
+}
+
+// ReadMeta reads a TaskMeta from a YAML file.
+func ReadMeta(path string) (*TaskMeta, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var meta TaskMeta
+	if err := yaml.Unmarshal(data, &meta); err != nil {
+		return nil, err
+	}
+	return &meta, nil
+}

internal/workspace/metadata_test.go

@@ -0,0 +1,121 @@
+package workspace
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestWriteAndReadMeta(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "task.yaml")
+
+	now := time.Now().UTC().Truncate(time.Second)
+	meta := &TaskMeta{
+		ID:            "20260405-143022",
+		Slug:          "arch-notes",
+		Title:         "arch notes",
+		CreatedAt:     now,
+		UpdatedAt:     now,
+		Status:        "active",
+		Category:      "general",
+		Mode:          "local",
+		Agent:         "claude",
+		WorkspacePath: "/home/warren/ai-workspaces/general/20260405_arch-notes",
+		ArchivedAt:    nil,
+	}
+
+	if err := WriteMeta(path, meta); err != nil {
+		t.Fatalf("WriteMeta: %v", err)
+	}
+
+	got, err := ReadMeta(path)
+	if err != nil {
+		t.Fatalf("ReadMeta: %v", err)
+	}
+
+	if got.ID != meta.ID {
+		t.Errorf("ID: got %q, want %q", got.ID, meta.ID)
+	}
+	if got.Slug != meta.Slug {
+		t.Errorf("Slug: got %q, want %q", got.Slug, meta.Slug)
+	}
+	if got.Status != "active" {
+		t.Errorf("Status: got %q, want \"active\"", got.Status)
+	}
+	if got.ArchivedAt != nil {
+		t.Errorf("ArchivedAt: expected nil, got %v", got.ArchivedAt)
+	}
+	if !got.CreatedAt.Equal(now) {
+		t.Errorf("CreatedAt: got %v, want %v", got.CreatedAt, now)
+	}
+}
+
+func TestMetaYAMLFieldsPresent(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "task.yaml")
+
+	now := time.Now().UTC().Truncate(time.Second)
+	meta := &TaskMeta{
+		ID:            "20260405-143022",
+		Slug:          "test",
+		Title:         "test",
+		CreatedAt:     now,
+		UpdatedAt:     now,
+		Status:        "active",
+		Category:      "general",
+		Mode:          "local",
+		Agent:         "claude",
+		WorkspacePath: "/tmp/test",
+	}
+
+	WriteMeta(path, meta)
+
+	data, _ := os.ReadFile(path)
+	content := string(data)
+
+	for _, field := range []string{"id:", "slug:", "title:", "created_at:", "updated_at:", "status:", "category:", "mode:", "agent:", "workspace_path:", "archived_at:"} {
+		if !strings.Contains(content, field) {
+			t.Errorf("missing field %s in YAML output", field)
+		}
+	}
+}
+
+func TestMetaArchive(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "task.yaml")
+
+	now := time.Now().UTC().Truncate(time.Second)
+	meta := &TaskMeta{
+		ID:            "20260405-143022",
+		Slug:          "test",
+		Title:         "test",
+		CreatedAt:     now,
+		UpdatedAt:     now,
+		Status:        "active",
+		Category:      "general",
+		Mode:          "local",
+		Agent:         "claude",
+		WorkspacePath: "/tmp/test",
+	}
+
+	WriteMeta(path, meta)
+
+	archiveTime := now.Add(time.Hour)
+	meta.Status = "archived"
+	meta.ArchivedAt = &archiveTime
+	WriteMeta(path, meta)
+
+	got, _ := ReadMeta(path)
+	if got.Status != "archived" {
+		t.Errorf("Status: got %q, want \"archived\"", got.Status)
+	}
+	if got.ArchivedAt == nil {
+		t.Fatal("ArchivedAt: expected non-nil")
+	}
+	if !got.ArchivedAt.Equal(archiveTime) {
+		t.Errorf("ArchivedAt: got %v, want %v", got.ArchivedAt, archiveTime)
+	}
+}