feat(help): add catalog for managing help topics

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkg/help/catalog.go

@@ -0,0 +1,87 @@
+package help
+
+import (
+	"fmt"
+)
+
+// Catalog manages help topics.
+type Catalog struct {
+	topics map[string]*Topic
+	index  *searchIndex
+}
+
+// DefaultCatalog returns a catalog with built-in topics.
+func DefaultCatalog() *Catalog {
+	c := &Catalog{
+		topics: make(map[string]*Topic),
+		index:  newSearchIndex(),
+	}
+
+	// Add default topics
+	c.Add(&Topic{
+		ID:    "getting-started",
+		Title: "Getting Started",
+		Content: `# Getting Started
+
+Welcome to Core! This CLI tool helps you manage development workflows.
+
+## Common Commands
+
+- core dev: Development workflows
+- core setup: Setup repository
+- core doctor: Check environment health
+- core test: Run tests
+
+## Next Steps
+
+Run 'core help <topic>' to learn more about a specific topic.
+`,
+	})
+	c.Add(&Topic{
+		ID:    "config",
+		Title: "Configuration",
+		Content: `# Configuration
+
+Core is configured via environment variables and config files.
+
+## Environment Variables
+
+- CORE_DEBUG: Enable debug logging
+- GITHUB_TOKEN: GitHub API token
+
+## Config Files
+
+Config is stored in ~/.core/config.yaml
+`,
+	})
+	return c
+}
+
+// Add adds a topic to the catalog.
+func (c *Catalog) Add(t *Topic) {
+	c.topics[t.ID] = t
+	c.index.Add(t)
+}
+
+// List returns all topics.
+func (c *Catalog) List() []*Topic {
+	var list []*Topic
+	for _, t := range c.topics {
+		list = append(list, t)
+	}
+	return list
+}
+
+// Search searches for topics.
+func (c *Catalog) Search(query string) []*SearchResult {
+	return c.index.Search(query)
+}
+
+// Get returns a topic by ID.
+func (c *Catalog) Get(id string) (*Topic, error) {
+	t, ok := c.topics[id]
+	if !ok {
+		return nil, fmt.Errorf("topic not found: %s", id)
+	}
+	return t, nil
+}