Better enable go extensions (#14)

* deps: run go mod tidy

* beads: Add public Go API for bd extensions

Implements a minimal public API to enable Go-based extensions without
exposing internal packages:

**New beads.go package:**
- Exports essential types: Issue, Status, IssueType, WorkFilter
- Provides status and issue type constants
- Exposes NewSQLiteStorage() as main entry point for extensions
- Includes comprehensive package documentation

**Updated EXTENDING.md:**
- Replaced internal package imports with public beads package
- Updated function calls to use new public API
- Changed sqlite.New() to beads.NewSQLiteStorage()
- Updated GetReady() to GetReadyWork() with WorkFilter

This enables clean Go-based orchestration extensions while maintaining
API stability and hiding internal implementation details.

* beads: Refine Go extensions API and documentation

Updates to the public Go API implementation following initial commit:

- Enhanced beads.go with refined extension interface
- Updated EXTENDING.md with clearer documentation
- Modified cmd/bd/main.go to support extension loading

Continues work on enabling Go-based bd extensions.

* Fix EXTENDING.md to use beads.WorkFilter instead of types.WorkFilter

The public API exports WorkFilter as beads.WorkFilter, not types.WorkFilter.
This fixes the code example to match the imports shown.

---------

Co-authored-by: Steve Yegge <steve.yegge@gmail.com>

beads.go

@@ -0,0 +1,137 @@
+// Package beads provides a minimal public API for extending bd with custom orchestration.
+//
+// Most extensions should use direct SQL queries against bd's database.
+// This package exports only the essential types and functions needed for
+// Go-based extensions that want to use bd's storage layer programmatically.
+//
+// For detailed guidance on extending bd, see EXTENDING.md.
+package beads
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/steveyegge/beads/internal/storage"
+	"github.com/steveyegge/beads/internal/storage/sqlite"
+	"github.com/steveyegge/beads/internal/types"
+)
+
+// Core types for working with issues
+type (
+	Issue      = types.Issue
+	Status     = types.Status
+	IssueType  = types.IssueType
+	WorkFilter = types.WorkFilter
+)
+
+// Status constants
+const (
+	StatusOpen       = types.StatusOpen
+	StatusInProgress = types.StatusInProgress
+	StatusClosed     = types.StatusClosed
+	StatusBlocked    = types.StatusBlocked
+)
+
+// IssueType constants
+const (
+	TypeBug     = types.TypeBug
+	TypeFeature = types.TypeFeature
+	TypeTask    = types.TypeTask
+	TypeEpic    = types.TypeEpic
+	TypeChore   = types.TypeChore
+)
+
+// Storage provides the minimal interface for extension orchestration
+type Storage = storage.Storage
+
+// NewSQLiteStorage opens a bd SQLite database for programmatic access.
+// Most extensions should use this to query ready work and update issue status.
+func NewSQLiteStorage(dbPath string) (Storage, error) {
+	return sqlite.New(dbPath)
+}
+
+// FindDatabasePath discovers the bd database path using bd's standard search order:
+//  1. $BEADS_DB environment variable
+//  2. .beads/*.db in current directory or ancestors
+//  3. ~/.beads/default.db (fallback)
+//
+// Returns empty string if no database is found at (1) or (2) and (3) doesn't exist.
+func FindDatabasePath() string {
+	// 1. Check environment variable
+	if envDB := os.Getenv("BEADS_DB"); envDB != "" {
+		return envDB
+	}
+
+	// 2. Search for .beads/*.db in current directory and ancestors
+	if foundDB := findDatabaseInTree(); foundDB != "" {
+		return foundDB
+	}
+
+	// 3. Try home directory default
+	if home, err := os.UserHomeDir(); err == nil {
+		defaultDB := filepath.Join(home, ".beads", "default.db")
+		// Only return if it exists
+		if _, err := os.Stat(defaultDB); err == nil {
+			return defaultDB
+		}
+	}
+
+	return ""
+}
+
+// FindJSONLPath returns the expected JSONL file path for the given database path.
+// It searches for existing *.jsonl files in the database directory and returns
+// the first one found, or defaults to "issues.jsonl".
+//
+// This function does not create directories or files - it only discovers paths.
+// Use this when you need to know where bd stores its JSONL export.
+func FindJSONLPath(dbPath string) string {
+	if dbPath == "" {
+		return ""
+	}
+
+	// Get the directory containing the database
+	dbDir := filepath.Dir(dbPath)
+
+	// Look for existing .jsonl files in the .beads directory
+	pattern := filepath.Join(dbDir, "*.jsonl")
+	matches, err := filepath.Glob(pattern)
+	if err == nil && len(matches) > 0 {
+		// Return the first .jsonl file found
+		return matches[0]
+	}
+
+	// Default to issues.jsonl
+	return filepath.Join(dbDir, "issues.jsonl")
+}
+
+// findDatabaseInTree walks up the directory tree looking for .beads/*.db
+func findDatabaseInTree() string {
+	dir, err := os.Getwd()
+	if err != nil {
+		return ""
+	}
+
+	// Walk up directory tree
+	for {
+		beadsDir := filepath.Join(dir, ".beads")
+		if info, err := os.Stat(beadsDir); err == nil && info.IsDir() {
+			// Found .beads/ directory, look for *.db files
+			matches, err := filepath.Glob(filepath.Join(beadsDir, "*.db"))
+			if err == nil && len(matches) > 0 {
+				// Return first .db file found
+				return matches[0]
+			}
+		}
+
+		// Move up one directory
+		parent := filepath.Dir(dir)
+		if parent == dir {
+			// Reached filesystem root
+			break
+		}
+		dir = parent
+	}
+
+	return ""
+}