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>

EXTENDING.md

@@ -99,12 +99,11 @@ func InitializeMyAppSchema(dbPath string) error {
 
 ```go
 import (
-    "github.com/steveyegge/beads/internal/storage/sqlite"
-    "github.com/steveyegge/beads/internal/types"
+    "github.com/steveyegge/beads"
 )
 
 // Open bd's storage
-store, err := sqlite.New(dbPath)
+store, err := beads.NewSQLiteStorage(dbPath)
 if err != nil {
     log.Fatal(err)
 }
@@ -115,7 +114,7 @@ if err := InitializeMyAppSchema(dbPath); err != nil {
 }
 
 // Use bd to find ready work
-readyIssues, err := store.GetReady(ctx, types.IssueFilter{Limit: 10})
+readyIssues, err := store.GetReadyWork(ctx, beads.WorkFilter{Limit: 10})
 if err != nil {
     log.Fatal(err)
 }
@@ -410,10 +409,17 @@ You can always access bd's database directly:
 import (
     "database/sql"
     _ "github.com/mattn/go-sqlite3"
+    "github.com/steveyegge/beads"
 )
 
+// Auto-discover bd's database path
+dbPath := beads.FindDatabasePath()
+if dbPath == "" {
+    log.Fatal("No bd database found. Run 'bd init' first.")
+}
+
 // Open the same database bd uses
-db, err := sql.Open("sqlite3", ".beads/myapp.db")
+db, err := sql.Open("sqlite3", dbPath)
 if err != nil {
     log.Fatal(err)
 }
@@ -429,6 +435,10 @@ err = db.QueryRow(`
 _, err = db.Exec(`
     INSERT INTO myapp_executions (issue_id, status) VALUES (?, ?)
 `, issueID, "running")
+
+// Find corresponding JSONL path (for git hooks, monitoring, etc.)
+jsonlPath := beads.FindJSONLPath(dbPath)
+fmt.Printf("BD exports to: %s\n", jsonlPath)
 ```
 
 ## Summary