Add RPC infrastructure and updated database

- RPC Phase 1: Protocol, server, client implementation
- Updated renumber.go with proper text reference updates (3-phase approach)
- Clean database exported: 344 issues (bd-1 to bd-344)
- Added DAEMON_DESIGN.md documentation
- Updated go.mod/go.sum for RPC dependencies

Amp-Thread-ID: https://ampcode.com/threads/T-456af77c-8b7f-4004-9027-c37b95e10ea5
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/client.go

@@ -0,0 +1,145 @@
+package rpc
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"net"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+)
+
+// Client is an RPC client that communicates with the bd daemon.
+type Client struct {
+	sockPath string
+	mu       sync.Mutex
+	conn     net.Conn
+}
+
+// TryConnect attempts to connect to the daemon and returns a client if successful.
+// Returns nil if the daemon is not running or socket doesn't exist.
+func TryConnect(sockPath string) *Client {
+	if _, err := os.Stat(sockPath); os.IsNotExist(err) {
+		return nil
+	}
+
+	conn, err := net.DialTimeout("unix", sockPath, 2*time.Second)
+	if err != nil {
+		return nil
+	}
+
+	client := &Client{
+		sockPath: sockPath,
+		conn:     conn,
+	}
+
+	if !client.ping() {
+		conn.Close()
+		return nil
+	}
+
+	return client
+}
+
+// ping sends a test request to verify the daemon is responsive.
+func (c *Client) ping() bool {
+	req, _ := NewRequest(OpStats, nil)
+	_, err := c.Execute(req)
+	return err == nil
+}
+
+// Execute sends a request to the daemon and returns the response.
+func (c *Client) Execute(req *Request) (*Response, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn == nil {
+		return nil, fmt.Errorf("client not connected")
+	}
+
+	reqJSON, err := json.Marshal(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal request: %w", err)
+	}
+
+	reqJSON = append(reqJSON, '\n')
+
+	if _, err := c.conn.Write(reqJSON); err != nil {
+		c.reconnect()
+		return nil, fmt.Errorf("failed to write request: %w", err)
+	}
+
+	scanner := bufio.NewScanner(c.conn)
+	if !scanner.Scan() {
+		if err := scanner.Err(); err != nil {
+			c.reconnect()
+			return nil, fmt.Errorf("failed to read response: %w", err)
+		}
+		c.reconnect()
+		return nil, fmt.Errorf("connection closed")
+	}
+
+	var resp Response
+	if err := json.Unmarshal(scanner.Bytes(), &resp); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal response: %w", err)
+	}
+
+	return &resp, nil
+}
+
+// reconnect attempts to reconnect to the daemon.
+func (c *Client) reconnect() error {
+	if c.conn != nil {
+		c.conn.Close()
+		c.conn = nil
+	}
+
+	var err error
+	backoff := 100 * time.Millisecond
+
+	for i := 0; i < 3; i++ {
+		c.conn, err = net.DialTimeout("unix", c.sockPath, 2*time.Second)
+		if err == nil {
+			return nil
+		}
+		time.Sleep(backoff)
+		backoff *= 2
+	}
+
+	return fmt.Errorf("failed to reconnect after 3 attempts: %w", err)
+}
+
+// Close closes the client connection.
+func (c *Client) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn != nil {
+		err := c.conn.Close()
+		c.conn = nil
+		return err
+	}
+	return nil
+}
+
+// SocketPath returns the default socket path for the given beads directory.
+func SocketPath(beadsDir string) string {
+	return filepath.Join(beadsDir, "bd.sock")
+}
+
+// DefaultSocketPath returns the socket path in the current working directory's .beads folder.
+func DefaultSocketPath() (string, error) {
+	wd, err := os.Getwd()
+	if err != nil {
+		return "", fmt.Errorf("failed to get working directory: %w", err)
+	}
+
+	beadsDir := filepath.Join(wd, ".beads")
+	if _, err := os.Stat(beadsDir); os.IsNotExist(err) {
+		return "", fmt.Errorf(".beads directory not found")
+	}
+
+	return SocketPath(beadsDir), nil
+}